Method of manufacturing corrugated laminate made of films

ABSTRACT

A laminate of thermoplastic polymeric films comprises at least one fluted ply A and at least one substantially flat ply B, adhered to one another in bonded zones along the flute crests. The wavelength of the flutes is preferably no more than 3 mm. Ply A has a generally uniform thickness or can have attenuated zones of lessor thickness extending parallel to the flute direction, each bonded zone being located mainly within an attenuated zone. The flutes can be sinuous with crests on both sides of ply A and can be adhered on each side to a ply B, in which case, attenuated zones can be on both sides and can have different widths. The flutes can be filled with filler material, including reinforcement strands, and one or both sides can be perforated. The method and apparatus employ aligned grooved fluting rollers and a grooved laminating roller.

RELATED APPLICATIONS

This application is: (1) a divisional of U.S. patent application Ser.No. 11/489,257 filed 19 Jul. 2006, which is a continuation of U.S.patent application Ser. No. 10/480,785 filed 15 Dec. 2003, published asUS2004017081 on Sep. 2, 2004, now U.S. Pat. No. 7,132,151 issued Nov. 7,2006, which is a 35 U.S.C. §371 Nationalization of PCT/EP02/007264 filedJun. 14, 2002, which claims priority to GB011469.9 filed 15 Jun. 2002;and (2) a divisional U.S. patent application Ser. No. 10/538,224 filed 7Nov. 2005, published as US20070257402 on 8 Nov. 2007, which is a 35U.S.C. §371 Nationalization of PCT/EP03/15001 filed 9 Dec. 2003, whichclaims priority to GB0229110.2 filed 13 Dec. 2002, GB 0304649.7 filed 28Feb. 2003 and GB 0319955.1 filed 26 Aug. 2003.

PCT/EP02/007264 DISCLOSURE BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a flexible laminate of films fromthermoplastic polymer material for applications in which relatively highyield strength and ultimate tensile strength is required, and a methodand apparatus for its manufacture.

Examples of such applications are: tarpaulins, pondliners, substitute ofgeotextiles, weather protective laminates, greenhouse film, industrialbags, carrier bags and self-standing pouches.

2. Description of the Related Art

For economical reasons there is an increasing need to reduce thethickness or square meter weight of flexible film made fromthermoplastic polymer material. The limits are partly set by therequired strength properties, and partly by the required self supportingcapability, i.e. stiffness with respect to banding. These needs havemainly been met by selected developments of the thermoplastic polymercompositions and as far as the strength is concerned also by biaxialorientation, or by crosslamination of films each of which exhibits agenerally monaxial or unbalanced biaxial orientation.

From strength point of view essential savings can be achieved by suchorientation and/or cross-lamination processes.

Thus as an example an industrial bag made from extruded polyethylenefilm of the best suited grades and destined for packing of 25 kgpolyethylene granules must generally have a thickness of 0.12-0.15 mm inorder to satisfy the normal strength requirements, while this thicknesscan be brought down to about 0.07 mm by use of optimized oriented andcross-laminated film from polyethylene. However, when thiscross-laminate is made in the known manner, few available types ofmachines for manufacturing bags from film, and few available types ofmachines for filling the bags, can work adequately with film which is sothin and flimsy.

A cross-laminate which, besides the improved strength propertiesobtained by the orientation and cross-lamination also by virtue of itsgeometrical structure shows significant improvements in this respect, isdescribed in the inventor's earlier Specification EP-A-0624126.

This is a cross-laminate of a slightly waved configuration in which thematerial of the curved crests on one or both sides of the laminate isthicker than elsewhere, the material between these thicker curved crestsbeing generally straightened out. (See FIGS. 1 and 2 of said patentpublications.) The structure is obtained by stretching between severalsets of grooved rollers under special conditions. This stretching alsoimparts transverse orientation. The disclosed wavelengths of the finalproducts are between 2.2 and 3.1 mm.

Cross-laminates according to the ‘said patent have been producedindustrially since 1995 for manufacture of industrial bags fromcombinations of high molecular weight high density polyethylene(HMWHDPE) and linear low density polyethylene (LLDPE) with film weightabout 90 gm⁻², and the slightly waved shape in combination with thethickened crests imparts a stiffness in one direction of the film whichhas proven to be very important for the performance of the bag machineswith such relatively thin film. However, the film is not adequate forwork with the 70 gm-² gauge which satisfies the strength requirements.

Furthermore the corrugated character of the film surface makes aparticularly fine print (as often required), impossible and also to someextent reduces the friction between filled bags in a stack, when thelayers of this stack are built up with the bags in crisscrossingarrangement as usually done.

As another example an agricultural tarpaulin (e.g. for protection ofcrops) made from a 70 gm⁻² cross-laminate of oriented polyethylene filmswould be a fully adequate substitute of a 100 gm⁻² tarpaulin made fromextrusion-coated woven tape, if only objective criteria were applied.However, in actual fact the average customer to agricultural tarpaulinsmakes his choice to a great extent on the basis of the “handle” and theappearance, and will reject the 70 gm⁻² tarpaulin due to its flimsiness,judging that it lacks substance.

The stiffness can of course always be increased by suitableincorporation of a filler, (and the present invention includes that asan additional option) but this will always more or less be at theexpense of puncture and tear propagation resistance, especially underimpact actions.

Object of the present invention is to add a “feel of substance” andimprove stiffness in laminates of films at least in one direction,without sacrificing the laminate's character of feeling and looking likea generally two-dimensional structure; furthermore without essentiallyharming the puncture and tear propagation resistance, and when desiredalso providing a good printability at least on one side of the laminate.

The basic idea behind the present invention is to apply the corrugatedpaperboard principle to laminates of thermoplastic films, but in such away that the flute structure is made extraordinarily fine(“minifluted”), so as to obtain a laminate which, in spite of thestructurally increased stiffness (at least in one direction), can stillsatisfy the above-mentioned conditions.

In itself the application of the corrugated paperboard principle to thethermoplastic film is not new, but the finest flute structure which hasbeen disclosed in patent literature, namely in U.S. Pat. No. 4,132,581col. 6, In. 66, is 50+/3 flutes per foot corresponding to a wavelengthof about 6.0 mm. It must also strongly be doubted that a wavelengthlower than this can be achieved by the method disclosed in the saidpatent, in which the first bonding process takes place under use of arow of many sealer bars supported and transported by a belt.

The sealer bars are transverse to the direction of movement (the machinedirection) so the fluting also becomes perpendicular to this direction.

The use of the method of the said U.S. patent is stated to bemanufacture of board material, and the thickness of the fluted ply isindicated to be about 0.004-0.025 inches (0.10-0.625 mm). In the exampleit is 0.018 inches (0.45 mm). Other patents dealing with the use of thecorrugated paperboard principle to thermoplastic film for the making ofpanels or boards are U.S. Pat. No. 3,662,736, U.S. Pat. No. 3,833,440,U.S. Pat. No. 3,837,973, EP-A-0325780 and WO-A-94/05498.

Japanese Patent Application Hei 02-052732 discloses laminates consistingof a corrugated thermoplastic film bonded to a flat thermoplastic film,which on its other side is bonded to paper. (The paper and flat sheetare first joined and then the corrugated film is added.) The flutes,which also in this case are perpendicular to the machine direction arepressed flat and adhesively closed at intervals so that a large numberof airtight vesicles are formed. The stated use of this product is forcushion material, sound insulating material, heat- and moistureinsulating material and wall decorative material. The thickness of thecorrugated sheet and flat sheet are not indicated, neither are thewavelength of the fluting and the length of the vesicles, but it ismentioned that the dimensions can be selected depending on the use ofthe laminate. However, it must be understood as implied that thewavelength in any case will be no lower than the lowest mentioned in theabove-mentioned U.S. Pat. No. 4,132,581 (i.e. about 6 mm). One reasonfor judging this is that this would not be advantageous for thementioned purposes, except for decoration, while another reason is thatthe disclosed apparatus would not be able to work with a lowerwavelength (i.e. a lower pitch of the gear rollers) except for making anextremely shallow and practically useless fluting. This is due to thefact that thermoplastic film is resilient and not permanently formableat ambient temperature which as implied by the presentation in thedrawing is used in the said method. If the pitch is Iowan the gearrollers which produce the fluting and the lamination, the corrugatedfilm will “jump out” of the grooves in the forming and laminating rollerduring its passage from the location where forming of flutes takes placeto the location where bonding takes place. The patent publication doesnot mention any means to hold the flutes in shape in the grooves of theroller.

In a conventional corrugator corrugated paperboard there are providedtracks or shield to hold the fluted paper in the grooves. At ambienttemperature this allows the paper to be more readily permanently formed.

Similar tracks or shields in unmodified form cannot be used withthermoplastic film under production conditions since friction againstthe track or shield quickly would create congestion by heating of thepolymer.

An improved, frictionless way of holding of flutes of paper in thegrooves of a roller is known from U.S. Pat. No. 6,139,938, namely bymaintaining a controlled under pressure within the grooves (see FIGS. 9and 10 and col. 7 lines 2534). This U.S. patent deals entirely withcorrugated paper laminates having particularly low wavelength whilemanufacture of corrugated structures from thermoplastic films is notmentioned. However, the improved method of holding the flutes will infact also, depending on the film thickness, be applicable to fine flutesin thermoplastic film. This was found in connection with the developmentof the present invention. However as mentioned above, the Japanesepatent application does not disclose any precautions to hold the flutesin shape in the grooves.

PCT/EP03/15001 DISCLOSURE BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a flexible laminate of films fromthermoplastic polymer material mainly for applications in whichrelatively high yield strength and ultimate tensile strength isrequired, and a method and apparatus for its manufacture. In specialaspect it also relates to film laminates which allow air but not waterto penetrate, and laminates with properties as filter material. Examplesof applications are: tarpaulins and cover-sheets, pond liners,substitute geotextiles, weather or gas protective garments, greenhousefilm, industrial bags or garbage bags, carrier bags, self-standingpouches, and sanitary backsheets.

2. Description of the Related Art

For economical reasons there is an increased need to reduce the squaremeter weight of flexible film made from thermoplastic polymer material.The limits are partly set by the required strength properties, andpartly by the required self supporting capability, i.e. stiffness orresilience with respect to bending. These needs have mainly been met byselected developments of the thermoplastic polymer compositions and asfar as the strength is concerned also by biaxial orientation, or bycross lamination of films each of which exhibits a generally monoaxialor unbalanced biaxial unorientation. From the strength point of viewessential savings can be achieved by such orientation and/orcrosslamination processes.

-   -   Thus as an example an industrial bag made from extruded        polyethylene film of the best suited grades and destined for        packing of 25 kg polyethylene granules must generally have a        thickness of 0.12-0.15 mm in order to satisfy the normal        strength requirements, while this thickness can be brought down        to about 0.07 mm by use of optimized oriented and crosslaminated        film from polyethylene. However, when this crosslaminate is made        in the known manner, few available types of machines for        manufacturing bags from film, and few available types of        machines for filling the bags, can work adequately with film        which is so thin and flimsy.

A crosslaminate which, besides the improved strength properties obtainedby the orientation and crosslamination, also by virtue of itsgeometrical structure shows significant improvements in this respect, isdescribed in the inventor's earlier specification EP-A-0624126.

This is a crosslaminate of a slightly waved configuration in which thematerial in the curved crests on one or both sides of the laminate isthicker than elsewhere, the material between these thicker curved crestsbeing generally straightened out. (See FIGS. 14 and 15 of said patentpublication). The structure is obtained by stretching between severalsets of grooved rollers under special conditions. This stretching alsoimparts transverse orientation. The disclosed wavelengths of the finalproduct are between 2.2 and 3.1 mm.

Crosslaminates according to EP-A-0624126 have been produced industriallysince 1995 for manufacture of industrial bags from combinations of highmolecular weight high density polyethylene (HMWHDPE) and linear lowdensity polyethylene (LLDPE) with film weight about 90 gm⁻². Theslightly waved shape in combination with the thickened crests imparts astiffness and resilience in one direction of the film which has provento be very important for the performance of the bag machines with suchrelatively thin film. However a film of a similar structure, but with a70gm⁻² gauge, which satisfies the strength requirements is too flimsyfor the making of bags.

As another example an agricultural tarpaulin (e.g. for protection ofcrops) made from a 70 gm crosslaminate of oriented polyethylene filmswould be a fully adequate substitute for a 100 gm⁻² tarpaulin made fromextrusion-coated woven tape, if only objective criteria were applied.However, the average customer of agricultural tarpaulins makes hischoice to a great extent on the basis of the handle and the appearance,and will reject the 70 gm ⁻² tarpaulin due to its flimsiness, judgingthat it lacks 3 a substance.

The stiffness can of course always be increased by suitableincorporation of a filler, (and the present invention includes that asan additional option) but this will always more or less be at theexpense of puncture and tear propagation resistance, especially underimpact.

SUMMARY OF THE INVENTION

The development of the particularly fine flute structure, the“miniflutes”, which is the object of the present invention has made thecorrugated paperboard principle applicable to completely differentfields of use such as the fields mentioned at the very beginning of thisspecification.

This has comprised a development of new types of machinery based ongrooved rollers with a very fine pitch. As it will appear from theexample the wavelength in a 90 gm⁻² “minifluted” 2-ply laminate (eachply about 45 gm⁻²) has in actual fact been brought down to 1.0 mmthrough a process which can be carried out industrially, and aftershrinkage of the flat ply transversely to the, flutes it has even beenbrought down to 0.8 mm. Especially by further use of shrinkage it canprobably be brought further down e.g. to about 0.5 mm. The mentioned2×45 gm⁻² corresponds to an average thickness of about 0.074 mm (2×0.037mm) if the laminate were pressed flat.

The invention is not limited to pressed-flat thicknesses around thisvalue, but also comprises, very generally speaking, minifluted laminatesof an average thickness in compacted form which is roughly about 0.3 mmor lower. Thicknesses down to 0.03 mm or even lower can be made forspecial purposes.

Nor is the invention limited to the use in connection withcross-laminates of oriented films. For different purposes differentcombinations of strength properties are required. Cross-laminates can,as is known, be produced with suitable combinations of severalcategories of strength properties but for many purposes other types ofstrength laminates may be preferable when the cost of the manufacturingprocess also is considered, and the present invention can also beuseful-in such other strength laminates as it further shall be specifiedbelow.

By making the wavelength as low as 3 mm or less, the laminate loses itscharacter of being a board material and gets appearance, handle andbending properties like a flexible film (see the example). It also getsimproved puncture properties, compared to laminates made from similarplies but with longer wavelength, since in the latter there is a largetendency for the plies to be ruptured individually instead ofcooperating in the resistance against the puncture.

The “minifluted” laminate also has the advantage that it can receive afine print on the flat side and a coarse print on the corrugated side.

Compared to non-corrugated laminates of the same composition and samesquare meter weight it feels much more substantial due to the increasedstiffness in one direction and due to the increased volume.

In the case of cross-laminates it is well-known that a weak bondingbetween the plies, or strong bonding or line-bonding, gives muchimproved tear propagation resistance, since it allows the tear toproceed in different directions in the different plies. Thereby thenotch effect is reduced. Since a cross-laminate with one ply corrugatedwill be line-bonded, it will show improved tear propagation resistance,no matter whether the wavelength is short or long, however“mini-fluting” makes the tear stop after a very short propagation, whichof course is very advantageous in most cases.

For the sake of good order, it should be mentioned that there alreadyhave been described “minifluted” laminates in literature, howeverlaminates of which at least the fluted ply consists of a material whichis not a thermoplastic film or an assembly of thermoplastic films.

Thus U.S. Pat. No. 6,139,938, which has been mentioned above, has forits object a 3-ply paper laminate with a corrugated paper sheet in themiddle and flat paper sheets on each side, like normal corrugated paperboard, however claimed to comprise 500-600 flutes per metercorresponding to a wavelength of 1.67-2.00 mm. This state purpose is toimprove the printability.

Japanese patent publication No. 07-251004 relates to an absorbingproduct in which a plane thermoplastic synthetic fiber sheet isthermally bonded to a corrugated sheet mainly consisting of activecarbon fibers. The wavelength of the corrugation is 2.5-20 mm.

Japanese patent publication No. 08-299385 relates to an absorbentlaminate consisting of a fluted non-woven fabric bonded on one side to aplane sheet or film, which can be a thermoplastic film. Between thesetwo plies there is nested a water-absorbing material. The wavelength isclaimed to be 3-50 mm, and it is stated that there would not besufficient space for the absorbing material if it were less. The productis for diapers and the similar products.

More precisely expressed the present invention concerns a laminatecomprising at least a monofilm-formed or multifilm-formed ply (A) andanother monofilm-formed or multifilm-form ply (B) both mainly consistingof thermoplastic polymer material, whereby at least A consists ofcold-orientable material in which A has a waved flute configurationwhile B is not waved, and B on a first side is adhesively bonded inbonding zones to the crests on a first side of A. A characterizingfeature of the laminate is that the wavelength of the said configurationis no more than 3 mm. The use of cold-orientable material in A isimportant for the strength of the product. Furthermore it is normallyimportant that the adhesive bonding has been established through alamination layer, so that melting of the main portions of A and B can beavoided during the lamination process, and that either the thickness ofA generally is the same within the non-bonded zones as it is within thebonded zones, or A exhibits zones which are attenuated in the solidstate and extend parallel to the flute direction in such a manner thateach bonding zone mainly is located within one of the attenuated zones.These attenuated zones will be referred to as the “first attenuatedzones” since there also may be further attenuated zones, as it shall beexplained later.

In this connection, an essential attenuation of A in the non-bondedzones, as compared to the thickness of A in the bonded zones, will ofcourse have a negative influence on the resistance to bending in thestiff direction (but it is generally easier to make the fluted laminateso). By contrast this resistance to bending is enhanced, seen in’relation to the average thickness of ply A, when each bonding zonemainly falls within one of these attenuated zones. The attenuated zonesalso facilitate the manufacturing process as it later shall beexplained. It is noted that while attenuation by stretching in themolten state reduces the tensile strength, attenuation by stretching insolid state increases the tensile strength in the direction in whichthis stretching has taken place.

While I here have identified the laminate as comprising the plies A andB, each “ply” can consist of one or more “films”, normally extrudedfilms, and each extruded film can and normally will consist of severalco-extruded “layers”. Thus the “lamination layer” through which thebonding takes place will normally be a co-extruded layer, however it canalso be a thin film applied in a conventional extrusion-laminationprocess.

While an upper limit of 3 mm wavelength has been chosen as a suitablevalue for distinguishing the product of the invention from corrugatedboard material, it is generally better to keep the wavelength within 2.5 mm, preferably within 2 mm and more preferably 1.5 mm. As alreadymentioned and shown in the example the inventor has been able to make it1.0 mm and under use of shrinkage after lamination even 0.8 mm.

As it appears from the introduction, the use of the present invention ismainly for strength film. This needs not always mean good strength inall directions; by contrast there are cases, e.g. in construction ofbags, where the focus should be on the strength in one direction,combined with a certain puncture and tear-propagation resistance. As anexample a conventional industrial bag of film thickness 0.160 mm madefrom a blend of 90% LOPE and 10% LLDPE will typically in itslongitudinal direction show a yield force of 20 Ncm⁻¹, i.e. a yieldtension of 12.5 MPa and in its transverse direction shows a yield forceof 16 Ncm⁻¹, i.e. a yield tension of 10.0 MPa.

Cross-laminated film material in average thickness 0.086 mm forheat-sealable bags developed by the inventor and manufactured inaccordance with the above-mentioned EPA-0624126 shows in its strongestdirection a yield force of 20 Ncm⁻¹, i.e. 23 MPa, and in its weakestdirection a yield force of 17 Ncm⁻¹, i.e. a yield tension of 20 MPa.

Since the invention in principle relates to flexible laminates for useswhere relatively high strength is required, although the emphasis of theinvention is on stiffness, feel and appearance, the yield tension of thelaminate in its strongest direction should normally be no less than 15MPa, preferably no less than 25 MPa. Correspondingly the ultimatetensile tension is conveniently about twice the said indicated values,or more. Here the cross section in mm is based on the solid materialonly, not including the air spaces, and it is an average, consideringthat ply A may have attenuated zones.

The yield tensions mentioned here refer to tensile testing at anextension velocity of 500% per minute. They are established fromstrain/stress graphs. These graphs will begin linear accordingly toHook's law, but will normally soon deviate from linearity although thedeformation still is elastic. In principle the yield tension should bethe tension at which the deformation becomes permanent, but thiscritical value, which is velocity dependent, is practically impossibleto determine. The way yield tension normally is determined in practice,and also considered determined in connection with the present invention,is the following:

In case the tension reaches a relative maximum, then remains constant ordecreases under continued elongation, later to increase again untilbreak occurs, the relative maximum of the tension is considered to bethe yield tension. The sample may also break at this point, and then theyield tension equals the ultimate tensile tension. If however thetension continues to increase with the continued elongation, but withmuch lower increases in tension per percentage elongation, then thestrain/stress curve after yield, and after it practically has become astraight line, is extrapolated backward to intersect with the line whichrepresents the Hook's-Law-part of the stretching. The tension at theintersection between the two lines is the defined yield tension.

An embodiment of the invention is characterized in that the ply A by thechoice of polymer material or by an incorporated filler or byorientation, within the non-bonded zones exhibits an average yieldtension parallel to the direction of fluting, which when it isdetermined as explained above, is no less than 30 Nmm⁻² (cross-sectionof ply A alone), preferably no less than 50 Nmm⁻² and still morepreferably no less than 75 Nmm⁻².

As already mentioned, A is preferably solid-state attenuated in zones(the “first attenuated zones”) and each bonding zone is mainly locatedwithin a first attenuated zone. These zones should be understood asdelimited by the positions where the thickness of A is an averagebetween A's lowest thickness within the first attenuated zone and A'shighest thickness within the adjacent non-bonded zone.

Another important embodiment of the invention is characterized in that Awithin each non-bonded zone and outside the first attenuated zone ifsuch zone is present (delimited as mentioned above) is molecularlyoriented mainly in a direction parallel to the direction of the flutesor a direction close to the latter as established by shrinkage tests.Such tests are commonly used. In this connection, a component oforientation in A perpendicular to the direction of the flutes will notcontribute to the yield tension in any direction, but will contribute tocertain other strength properties.

A preferable limitation of the extension of each first attenuationzone—preferable with a view to the stiffness in one direction—is alaminate in which said first attenuated zones are present in Acharacterized in that each such zone of attenuated A, if it extendsbeyond the corresponding zone of bonding into a non-bonded zone of A, islimited to a width which leaves more than half of and preferably no lessthan 70% of the width of the non-bonded zone, as not belonging to anyfirst attenuated zone, this width being measured along the curvedsurfaces, and the preferable thickness of these zones are specified in alaminate characterized in that said first attenuated zones of A areattenuated so that the minimum thickness in that zone is less than 75%of the maximum thickness of A in the non-bonded zone, preferably lessthan 50% and more preferably less than 30% of that maximum thickness.

Additionally to the first attenuated zones it can be very advantageousto have a second solid-state-attenuated zone (hereinafter the secondattenuated zone) between each pair of adjacent first attenuated zones.These second attenuated zones should be narrower than the first onespreferably as narrow as possible but also alternated so that thethickness of A in the zone is as thin as possible—and located on thecrests of A on the side opposite to the bonded zones. They act as“hinges”, and if they are made narrow and deep enough they improve thestiffness since the cross-section of A becomes zig-zagging instead ofsmoothly waved (as described further in connection with FIG. 3) and Aand B thereby form triangular structures. They also essentiallyfacilitate the manufacturing process, which is explained below.

In addition to the improvements in stiffness caused by the first andsecond attenuated zones (improvements seen in relation to the averagethickness of A) each set of zones also normally improves the resistanceagainst shock actions, i.e. they normally improve impact strength,shock-puncture resistance and shock-tear-propagation resistance. This isbecause there is started a stretching (or further stretching if Aalready was stretched) and this stretching normally has a tendency toprogress under shock actions, whereby the first and second attenuatedzones can act as shock-absorbers.

Normally the wavelength of each flute including an adjacent bonding zoneshould be no longer than 50 times the highest thickness of A within theflute, preferably no more than 40 times and still more preferably nomore than 30 times the said thickness. As an example, if the highestthickness of A is 0.037 mm as in the operative example below, thementioned values correspond to wavelengths of 1.85, 1.48 and 1.11 mmrespectively.

In order to “integrate” the plies conveniently with each other in orderfor strength purposes, the width of each bonding zone should normally beno less than 15%, preferably no less that 20% and still more preferablyno less than 30% of the wavelength, and in order to achieve asubstantial effect of the fluting, the width of each non-bonded zone ofA as measured between the two adjacent bonding zones and measured alongits curved surface, should preferably be no less than 10% and preferablyno less than 20% longer than the corresponding linear distance. This isa measure of the depth of the flutes.

For many purposes, e.g., when increased stiffness against bending is alldirections is wanted, there can be a non-waved monolayered ormultilayered film C on the side of A which is opposite to B as specifiedin a laminate characterized in that it comprises a further non-wavedmonofilm formed or multifilm formed ply (C) of thermoplastic polymermaterial, C being bonded to the crests of A on the second side of thelatter through a lamination layer.

A fluted outside surface on a bag has a mentioned above a disadvantage,namely in connection with printed and stacking of the filled bag.However there are articles in which the special roughness of a flutedsurface can be very advantageous in use e.g. on mats. For such articlesthere can advantageously be two waved mono- or multilayered plies (A)and (D) laminated to the two opposing sides of the non-waved mono- ormultilayered film (b), as specified in a laminate characterized in thatit comprises a further monofilm formed or multifilm formed ply (D)consisting of thermoplastic, cold-orientable polymer material, said plyhaving waved flute configuration, the crests on one side of D beingbonded to the second side of B through a lamination layer, and thewavelength of D's flute configuration preferably being no more than 3mm.

The films A, B, C and D will normally consist of polyolefin and willnormally be produced by a process which involves extrusion. This willnormally be a co-extrusion process by which lamination layers andoptionally heat-seal layers are joined with the main body of the film.

At least some of the flutes can be flattened at longitudinally spacedintervals and preferably bonded across the entire width of each flute atthe flattened locations to make the flutes form a row of narrow closedelongated pockets. Preferably the flattened portions of a number ofmutually adjacent flutes or of all flutes form a series of linestransverse to the longitudinal direction of the flutes. This can makethe corrugated laminate look and feel more textile-like, almost make theimpression of a woven structure, and make it more flexible in thedirection which otherwise is stiff, without losing the feel of bulk andsubstance. Flattening can also be used to create preferential locationsfor bending.

Further description of different embodiments of the product and ofparticular uses will follow after the description of the method.

In accordance with the above characterization of the laminate of theinvention, the method of manufacture which takes place under the use ofa grooved roller for formation of the flutes, and also under use of agrooved roller for the lamination by heat and pressure (which in certaincase can be the same grooved roller) is characterized in that thedivision on the roller which produced the lamination is at the highest 3mm. The new method according to the invention is a method ofmanufacturing a laminate or monofilm formed or multifilm formed ply (A)with another monofilm formed or multifilm formed ply (B) both consistingof thermoplastic polymer material in which A has a waved fluteconfiguration while B is not waved, and B on a first side is adhesivelybonded in zones to the crests on a first side of A, in which further thewaved flute structure is formed by the use of a grooved roller, and thesaid bonding with B is carried out under heat and pressure and alsounder use of a grooved roller, and at least A is selected as mainlyconsisting of solid-state orientable material, characterized in that thedivision on the grooved roller which produces the lamination on the saidcrests is at the highest 3 mm.

New apparatus for carrying out the method is an apparatus for forming alaminate comprising feeding means for feeding a continuous web of ply Bformed of a thermoplastic material from a supply to a laminatingstation; a grooved fluting roller for imposing a waved fluted structureon a ply of thermoplastic material; feeding means for feeding acontinuos web of ply A formed of a thermoplastic material from a supplyto the grooved fluting roller and thereafter to the laminating stationin face to face relationship with ply B; wherein the laminating stationcomprises a grooved laminating roller which is capable of applying heatand pressure between the crests of the flutes of ply A and ply B so asto bond the contacting surfaces of ply A and ply B in bonding zones toform a laminate product; characterized in that the division between thecrests of the laminating roller is no more than 3 mm.

The apparatus can be adapted either to make the flutes generallyperpendicular to the machine direction as in conventional manufacture ofcorrugated laminates, or generally parallel to the machine direction.This will be specified below.

Normally the bonding is established through a lamination layer (producedby co-extrusion or by an extrusion lamination technique) in order toavoid weakening and normally the steps of the process are adapted eitherto avoid any significant attenuation of the zones in A, or alternativelya stretching in solid state between a set of grooved rollers is adaptedto produce the above-mentioned “first attenuated zones”, whereby thegrooved roller for lamination is coordinated with the set of groovedrollers for stretching in such a way that each zone of bonding mainlybecomes located within a first attenuated zone.

The “second attenuated zones”, which have been described above in thedescription of the product, can be formed by stretching between afurther set of grooved rollers suitably coordinated with the groovedrollers which produce the first attenuated zones.

The advantages of the first and second attenuated zones in terms ofproduct properties have already been explained. For the carrying out ofthe method, the first attenuated lines allow increases of velocity andtherefore improved economy, since the zones in ply A which are going tobe bonded, have been made thinner and therefore require less heatingtime during the application of heat prior to the bonding. Furthermorethe first attenuated zones and in particular the combination of firstand second attenuated zones can be of great help for the process byacting as “hinges” in ply A. In the type of apparatus in which thegrooved roller for lamination has grooves which are generally parallelwith its axis, these “hinges” make it possible to direct even relativelyheavy A-ply into fine grooves. In the type of apparatus in which thegrooves are circular or helical, but in any case approximatelyperpendicular to the roller axis, the “hinges” help to keep ply A “intrack” during its passage from grooved roller to grooved roller in otherworks the “hinges” help to coordinate the action of the groovedlamination roller with the action of the preceding set or sets ofgrooved rollers which form the flute under a simultaneous transversestretching.

While it is essential for normal uses of the invention for applicationsas a flexible film that the division on the grooved roller whichproduces the lamination on the crests is no more than 3 mm, it isgenerally recommendable to make it no more than 2.5 mm, preferably nomore than 2.0 mm and still more preferably no more than 1.5 mm.

The film or films used for ply A is preferably, prior to forming of thewaved configuration and prior to making of the first and secondattenuated zones (if such zones are made), supplied with orientation inone or both directions, the resultant main direction of orientationbeing in the direction which is selected to become the direction offluting. This can be by means of a strong melt orientation, orpreferably, alternatively or additionally by known stretching procedurescarried out in the solid state. If the process is adapted to make theflutes generally parallel with the machine direction, this will be agenerally longitudinal orientation process, which is simple, and if theprocess is adapted to make the flutes generally perpendicular to themachine direction, it will be a generally transverse orientation processwhich is much more complicated to establish and usually requiresexpensive machinery. It is noted that neither of the two closestreferences, i.e. U.S. Pat. No. 4,132,581 and Japanese patent applicationHei 02-052732 have disclosures which indicate that ply A could beoriented in a direction generally parallel with the flutes. In these twopublications the flutes are formed in the transverse direction, and hadthere been thought of using transversely oriented film it would havebeen natural to mention this since without special steps the film is notformed so in the extrusion or casting process.

As it already has been described in connection with the product, afurther non-waved monofilm formed or multifilm formed ply (C) ofthermoplastic polymer material can simultaneously with or subsequent tothe bonding of B to A be adhesively bonded to the crests of A on thesecond side of A. Another useful possibility is that, in a mannersimilar to the forming and application of A, there is produced a secondmonofilm formed or multifilm formed ply (D) having waved fluteconfiguration with a wavelength of preferably no more than 3 mm, and thecrests on one side of D are laminated to the second side of Bsimultaneously with or following the lamination of B with A.

In most applications of the invention the mono- or multifilm formedplies should mainly consist of polyolefin, and should be produced by aprocess involving extrusion. Furthermore the films constituting theplies should normally be made by co-extrusion in which there iscoextruded surface layers to enable the lamination without any meltingof the main body of the films.

As it also appears from the description of the product some of theflutes at least can be flattened after the lamination. This is done atintervals, preferably under heat and pressure sufficient to bond allfilms in the laminate to each other so that the flutes with adjacentfilm material form fine elongated pockets closed at each end. Theflattening can be carried out with bars or cogs which have theirlongitudinal direction arranged transversely to the flute direction andwhich each covers a number of flutes, optionally the entire width of thelaminate.

A suitably distinct formation of the first attenuated zones can beestablished at least in part by giving the crests on the groovedstretching roller intended to produce the stripes a temperature which ishigher than the temperature of the crests on the other groovedstretching roller and/or by giving the crests on the grooved stretchingroller intended to produce the stripes a radius of curvature which issmaller than the radius of curvature of the crests on the matchinggrooved stretching roller. A significant orientation mainly in thedirection nearly parallel with the fluting, and/or a high co-efficientof elasticity (B) of ply A are also efficient means to give the firstattenuated zones suitably distinct borders.

A good way to make the fluting finer than this can be done by purelymechanical means is by use of shrinkage. Prior to the lamination ply Bis supplied with orientation generally perpendicular to the directionwhich becomes direction of fluting and after the lamination B issubjected to shrinkage in a direction generally perpendicular to thedirection of fluting.

As it already has been stated the waved flute structure can be formed indifferent directions. Thus it can be established mainly in A'slongitudinal direction under a generally transverse orientation processby taking A through a set of driven mutually intermeshing groovedrollers, the grooves of the rollers being circular or being helical andforming an angle of at least 60° with the roller axis. It is mostpractical to make this angle about 90° or at least very close to this.This can be arranged “so that A moves directly from its exit from one ofthe grooved stretching rollers which form the waving on A to the groovedlamination roller, whereby these two grooved rollers are in closeproximity to each other and have the same pitch, and are mutuallyadjusted in the axial direction. The pitch, in this aspect should bemeasured at the operational temperature of the respective roller.

Alternatively A can move from this exit from one of the groovedstretching rollers which form the waving on A to the grooved laminationroller over one or a series of heated, grooved transfer rollers. Thegrooved rollers in this row start with the grooved stretching rollersand end with the grooved lamination roller and each is in closeproximity to its neighbor or neighbors. Each of the grooved rollers inthe row” has the same pitch (measured at the operational temperature ofthe respective roller) and their axial positions are adjustable to eachother (see FIGS. 7 and 8 and the example).

When the fluting is produced in the longitudinal direction by means ofrollers with circular grooves, ply A's width measured as the direct,linear distance will remain constant from its inlet to the process ofthe lamination, apart from deviations in very narrow edge regions, whichshould be trimmed off. Therefore, the ratio between ply A's real width,measured along its curved extension, and A's linear width, which is thesame as B's width, equals the transverse stretch ratio and is related tothe thickness reductions in the attenuated zones.

However, as it already has been mentioned, the flutes can also beproduced in a distinctly transverse direction. In this embodiment, anangle of about 30° between the grooves and the roller axis is probablyabout the maximum which is practically possible, but it is simplest towork with grooves which are parallel with the roller axis.

The embodiment with grooves parallel to the roller axis is furtherdefined in a method further characterized in that each grooved rollerused to form the flutes in A and A to B, and each grooved roller used toform the first attenuated zones as described herein if such zones areproduced, and each grooved roller used to form the second attenuatedzones as described herein if such zones are formed, is a grooved rollerin which the grooves are essentially parallel with the roller axis, andmeans are provided to hold the flutes of A in the grooves in the rolleron which these flutes are formed and bonded during the passage from theposition where the flutes are formed to the position where A is bondedto B, said holding means adapted to avoid a frictional rubbing on Aduring said passage. The method can be further characterized in that theflutes in A are formed by use of an air jet or a transverse row ofairjets which directs A into the grooves on the forming roller. Themethod can be further characterized in that if first attenuated zonesare formed as described herein by grooved rollers acting in coordinationwith the grooved roller used for lamination, said coordination consistsin an automatic fine regulation of the relative velocities between therollers. The method can be further characterized in that when secondattenuated zones are formed as described herein by grooved rollersacting in coordination with the grooved rollers used to produce thefirst attenuated zones, said coordination consists in an automatic fineregulation of the relative velocities between the rollers.

The means to hold A in fluted form in the grooves from flute formationto bonding, and adapted to avoid a frictional rubbing on A, can bedevices for suction through channels from the inside of grooved roller—amethod which as already mentioned is known from making corrugatedpaperboard—or it can be use of tracks or shields which are adapted fromthe construction used in manufacture of corrugated paperboard by beingair-lubricated. This means that the tracks or shields are supplied withfine channels, or preferably a part of each track or shield is made fromporous, sintered metal, and pressurized air is blown through thechannels or pores to form an air-film on which the fluted ply can flow.

The means for fine regulation comprise a method characterized in that iffirst attenuated zones are formed as described herein by grooved rollersacting in coordination with the grooved roller used for lamination, saidcoordination consists in an automatic fine regulation of the relativevelocities between the rollers and a method characterized in that whensecond attenuated zones are formed as described herein by groovedrollers acting in coordination with the grooved rollers used to producethe first attenuated zones, said coordination consists in an automaticfine regulation of the relative velocities between the rollers, whichare similar to registration means in multicolor printing technology.

The following sections will describe different selections of theorientation and/or elasticity in the different plies, specialutilization of the channels or pockets formed by the flutes, andparticular end uses of the product of the invention.

It has already been mentioned that, in an important embodiment of theproduct according to the invention, ply A within each non-bonded zoneand outside the first attenuated zone if such zone is present, ismolecularly oriented mainly in a direction parallel to the direction ofthe flutes or a direction close to the latter.

With ply A so oriented, there are different preferable options for plyB, depending on the uses of the laminate. One very important option isthat B also is molecularly oriented and B's orientation within eachnon-bonded zone in a direction perpendicular to the direction of theflutes is higher than A's average orientation in the same directionwithin the non-bonded zone. The said two components of orientation arealso in this case, indicated by shrinkage tests.

This does not necessarily mean that ply B must have its strongestcomponent of orientation in the transverse direction, in other words thelaminate need not necessarily be a cross-laminate. Thus, ply B maysimply be highly blown film, which by means of a high blow ratio hasobtained a relatively high transverse melt orientation. The embodimentis further characterized in that the yield tension in A in a directionperpendicular to the flutes, both referring to the cross-section of therespective ply and determined in the non-bonded zones on narrow stripsat an extension velocity of 500% min⁻¹, is no less than 30 Nmm⁻² andstill more preferably no less than 75 Nmm⁻².

As mentioned there are cases, e.g., in bag construction, in which thereis a need for a high yield tension in one direction only, but combinedwith high puncture resistance. The laminate characterized in that B hasa lower coefficient of elasticity than A, both as measured in thedirection perpendicular to the flute direction or the laminatecharacterized in that the choice of B and of depth of fluting is so thatby stretching of the laminate perpendicular to the direction of thefluting up to the point where the waving has disappeared, B still hasnot undergone any significant plastic deformation, preferably B isselected as a thermoplastic elastomer are designed for this.

As it appears from the foregoing the present invention is very useful inconnection with cross-laminate, i.e. the laminate which comprises atleast two films each of which has a main direction of orientation andwhich are laminated so that the said two directions cross each other.Different ways of carrying out this aspect of the inventions are asdescribed below, from which also the method of making becomes clear: (1)a laminate characterized in that A and B each has a main direction oforientation, either by being uniaxially oriented or unbalanced biaxiallyoriented, or by in itself being a cross-laminate of uniaxially orientedor unbalanced biaxially oriented films, such cross-laminate exhibiting aresultant main direction of orientation, whereby the resultant maindirection of orientation in A is generally parallel with thelongitudinal direction of the flutes, while the resultant main directionof orientation in B forms an angle to the said direction in A; (2) alaminate characterized in that B and C each has a main direction oforientation, either by being uniaxially oriented or unbalanced biaxiallyoriented, or each in itself being a cross-laminate of uniaxially orunbalanced biaxially oriented films, said cross-laminate exhibiting aresultant main direction of orientation whereby the main direction oforientation in B crisscrosses the main direction of orientation in C;(3) a laminate characterized in that A in a non-oriented state exhibitsa co-efficient of elasticity E which is lower than E of both B and C innon-oriented state, preferably by a factor of at least 1.5 and morepreferably at least 2; and (4) a laminate characterized in that theflutes are flattened at intervals and bonded across each ones entirewidth to make the flute form a row of narrow closed pockets.

Suitable methods and apparatus for cross-lamination may be achieved bycombining the information in the above mentioned EP-A-0624126, mainly inits introduction, with the formation in the inventor's olderGB-A-1526722. Thus, with reference to FIG. 4 of the present drawings,Band C may each be films, including laminates, which exhibit a maindirection of orientation whereby B's main direction of orientationcriss-crosses with C'S main direction of orientation. One of thesedirections may be parallel with the machine direction, the otherperpendicular thereto, or both may from an angle higher than and lowerthan 90°, preferably between 20° and 70° and more preferably in therange 25°-65° with the machine direction. In this arrangement the wavedA supplies to the laminate stiffness against bending, but at the sametime, since it establishes a “dislocated” bonding between Band C, italso has importance for the tear propagation resistance. It is knowne.g. from the above-mentioned GB-A-1.526722, that the superior tearpropagation resistance which can be obtained by cross-lamination,depends on having bonding strength which is not too high, since the tearmust be allowed to develop along different directions in the differentplies of the cross-laminate. Since on the other hand the cross-laminateshould not be prone to accidental delamination during use, as forinstance described in the said patent, there can be used a combinationof strong bonding in spots or lines and a weak bonding over the rest.However, the “dislocated” bonding of cross-laminated Band C through thewaved A can provide a better combination of high tear propagationresistance and adequate bonding strength, especially when thecoefficient of elasticity E of film A is lower than the coefficient Efor ‘both Band C, preferably by a factor of at least 1.5 and morepreferably at least 2. Furthermore the flutes may be flattened atintervals and bonded across each ones entire width to make the flutefrom a row of narrow, closed pockets. The purposes of such flatteninghave been mentioned above.

In the above description there is mentioned the “main direction oforientation” in the films Band C. If plies Band C each are mono-films,normally with coextruded surface layers, this may be a monoaxial orunbalanced biaxial orientation. However, each of the films Band C mayalso in themselves be cross-laminates. normally 2-ply cross-laminates.

To clarify this, B may e.g. consist of two plies of equal composition,equal thickness and equal degree of orientation, but one oriented at+30° and the other at −30° to the machine direction. This will result ina main direction of orientation following the machine direction.Similarly C may consist of two equal plies, one oriented at +60° and theother at −60°. The resultant direction of orientation then isperpendicular to the machine direction.

Uniaxial or unbalanced orientation in a film can be obtained under useof spiral cutting of a tubular film with mainly longitudinal directionas disclosed in EP-A-0624126 and GB-A-1526722, both mentioned above, anddisclosed in more detail in EP-A-0426702. The latter also discloses amethod of obtaining a uniaxial or strongly unbalanced melt-orientationwhich is perpendicular to the machine direction, namely by twisting of atubular film coming out of the extrusion die followed by helical cuttingunder the calculated angle. Another embodiment of the cross-laminationaspect off the present invention is a laminate characterized in that Aand B each has a main direction of orientation, either by beinguniaxially oriented or unbalanced biaxially oriented, or by in itselfbeing a cross-laminate of uniaxially oriented or unbalanced biaxiallyoriented films, such cross-laminate exhibiting a resultant maindirection of orientation, whereby the resultant main direction oforientation in A is generally parallel with the longitudinal directionof the flutes, while the resultant main direction of orientation in Bforms an angle to the said direction in A. The expression resultant maindirection of orientation has the same meaning as explained above.

If this laminate is to be used in the construction of bags withheat-seals generally perpendicular to the direction of the flutes, andif such heat-seals may be subjected to high shock-peel forces then thelaminate should preferably be constructed as a laminate characterized inthat there is only the two mono- or multilayered films A and B and A isunoriented states exhibits a co-efficient of elasticity E which is lowerthan the E exhibited by B in unoriented state, preferably by a factor ofat least 1.5 and more preferably by a factor of at least 2. The flutedsofter A-film can then form the inner side for heat-sealing, and thestiffer, smooth B-film can form the outer side of the bag.

Another aspect of the invention (“the encapsulation/canalizationaspect”) comprises a number of embodiments which for different practicalpurposes utilize the interior cavities in the laminate, optionally incombination with suitable perforations, either to canalize a flow ofliquid or air, or to encapsulate filling material in particulate,fibrous, filament or liquid form. The latter may e. g. be a preservativefor goods packed in the flexible laminate. These different embodimentsare described in the following descriptions. The laminate ischaracterized in that at least some of the channels formed by the flutesand the matching non-waved film material, which channels may be closedto pockets, contain a filling material in particulate, fibrous, filamentor liquid form. Such laminates can also be characterized in that saidfilling material is adapted to act as a filter material by holding backsuspended particles from a liquid passing through the channels orpockets or is an absorbent or ion exchanger capable of absorbing orexchanging matter dissolved in such liquid, said filler optionally beingfibre-formed or yarn-formed, and that each filled flute and matchingnon-waved film material is supplied with a row of perforations, wherebythe perforations or groups of perforations in a flute and theperforations or groups of perforations in the matching non-waved filmmaterial are mutually displaced so as to force the liquid with thesuspended particles, while passing from one surface of the laminatetowards the other surface, to run through the filter material in adirection parallel to the longitudinal directions of the flutes.Geotextile substitute can also be constructed that are capable ofletting water through but withholding the soil and preferably comprisingoriented and crosslaminated films. Such geotextile substitutes arecharacterized in that said filling material is adapted to act as afilter material by holding back suspended particles from a liquidpassing through the channels or pockets or is an absorbent or ionexchanger capable of absorbing or exchanging matter dissolved in suchliquid, said filler optionally being fiber-formed or yarn-formed, andthat each filled flute and matching non-waved film material is suppliedwith a row of perforations, whereby the perforations or groups ofperforations in a flute and the perforations or groups of perforationsin the matching non-waved film material are mutually displaced so as toforce the liquid with the suspended particles, while passing from onesurface of the laminate towards the other surface, to run through thefilter material in a direction parallel to the longitudinal directionsof the flutes. Geotextile substitute are further characterized in thatthe filler is sand. The method of making these products are described inthe following descriptions. The method is characterized in thatparticulate, liquid or thread/yarn formed material is filled into someat least of those flutes in A which, by the lamination to B, are closedto form channels, this filling taking place before, prior to or duringsaid lamination. The method can also be characterized in that afterfilling the filled channels are closed at intervals by pressure and heatto form filled pockets. The method can also be characterized in thatprior to, simultaneously with or following the filling step perforationsare made in the laminate at least on one side to help the fillingmaterial or part thereof dissipate into the surroundings or to allow airor liquid to pass through the pack of filling material. The method canalso be characterized in that there is made a row of micro perforationson each side of each filled channel, said rows being mutually displacedto force air or liquid which passes through the laminate to run adistance along a channel or pocket, and apparatus suitable for carryingout the method is described in the following description. The apparatuscomprising a filler station between the fluting roller (s) and thelaminating roller for introducing filling material into the flutesbetween ply A and ply B. The filling station can also operate in whichthe filler material is in particulate, fibrous or yarn form.

The embodiment of the present invention in which the fine canals or“pockets” are used to “bury” preservatives, have obvious advantages overthe usual method of blending such agents with the polymers to beextruded into film form. One advantage is that the concentration of thepreservative can be much higher, another that the preservative needs notbe able to withstand the temperature of extrusion. The preservative mayreach the object to be preserved by migration alone, or if the agent issolid it may gradually evaporate and diffuse through sufficiently fineperforations or pores.

It is also customary to contain preservative agents in small bags whichare placed inside a package this method of protection, the presentinvention has the advantage that the preservative agent can bedistributed almost homogeneously over the full area of the packingmaterial.

The filter material in the laminate is characterized in that saidfilling material is adapted to act as a filter material by holding backsuspended particles from a liquid passing through the channels orpockets or is an absorbent or ion exchanger capable of absorbing orexchanging matter dissolved in such liquid, said filler optionally beingfibre-formed or yarn-formed, and that each filled flute and matchingnon-waved film material is supplied with a row of perforations, wherebythe perforations or groups of perforations in a flute and theperforations or groups of perforations in the matching non-waved filmmaterial are mutually displaced so as to force the liquid with thesuspended particles, while passing from one surface of the laminatetowards the other surface, to run through the filter material in adirection parallel to the longitudinal directions of the flutes has manypotential uses, e.g. as a geotextile (geotextile substitute capable ofletting water through but withholding the soil, constructed accordingand preferably comprising oriented and cross-laminated films, where thefiller is sand) but also for instance for water treatment in thechemical industry and in gas face masks.

Although the claims relating to these filter materials, including theweather-protective laminate is made to be weather (rain and wind)resistant and air-permeable, characterized in that at least some of thechannels formed either by waved ply A and non-waved ply B and/or Cand/or waved ply D are connected to the environment on both sides of thelaminate through perforations, the perforations on the two sides of achannel being mutually displaced so as to force air or water which passthrough the laminate to run a distance through a channel, it should beunderstood that similar products having wavelength somewhat higher than3 mm also have important uses and are considered inventive new products.Thus in a further aspect of the invention there is provided a laminatecomprising at least a monofilm formed or multifilm formed ply (A) andanother monofilm formed or multifilm formed ply (B) both mainlyconsisting of thermoplastic polymer material, whereby at least Aconsists of cold-orientable material in which A has a waved fluteconfiguration while B is not waved, and B on a first side is adhesivelybonded in bonding zones to the crests on a first side of A in which theadhesive bonding has been established through a lamination layer, andthat either the thickness of A is generally the same within thenon-bonded zones as it is within the bonded zones, or A exhibits firstsolid-state-attenuated zones (hereinafter the first attenuated zones)extending parallel to the flute direction, each bonding zone mainlybeing located within a first attenuated zone, the laminate beingmoisture resistant but air permeable. The laminates are useful forforming raincoats and tarpaulins. Other uses in which an additive isincorporated into the flutes are described below.

Other important uses of the invention are for bags and self-standingpouches. In this connection, reference is made to the followingproducts: (1) a bag made from the laminate of this inventioncharacterized in that the laminate comprises only the two mono- ormultifilm formed plies A and B, and in that the bottom and top of thebag are generally perpendicular to the longitudinal direction of theflutes; (2) a self-standing bag or pouch made from the laminate of thisinvention, in which the bottom of the bag or pouch is gusseted, andfront and back faces of the bag or pouch are adhesively joined at theiredges preferably by heat-sealing, characterized in that the laminatecomprises only the two mono- or multifilm formed plies A and B, and inthat the bottom and top of the bag or pouch are generally parallel withthe longitudinal direction of the flutes; and (3) a self-standing bag orpouch characterized in that the capability of the bag or pouch to standon its own is enhanced by flat-pressed lines generally perpendicular tothe longitudinal direction of the flutes.

For all uses of the present invention, a very interesting andwear-resistant print can be obtained when, prior to the lamination, Aand/or B is supplied with print on the surface to become the inside ofthe laminate, the printing process being in register with theflute-forming and lamination processes so as to limit the printgenerally to the non-bonded zones. This durable print may form a text, adecorative pattern or simply lines which accentuate the fluting or thetextile-like appearance of the laminate. Special decorative effects canbe achieved if the print provides a metallic appearance or amother-of-pearl effect.

PCT/EP03/15001 DISCLOSURE SUMMARY OF THE INVENTION

An object of the present invention is to add a “feel of substance” andimprove the stiffness or resilience of the film in all directions,without sacrificing the laminate's character of feeling and looking likea generally two-dimensional structure, and without essentially harmingthe puncture and tear propagation resistance.

The basic idea behind the present invention is to apply the corrugatedpaperboard principle to laminates of thermoplastic films, but preferablyin such a way that the flute structure is especially fine(“minifluted”), so as to obtain a laminate which, in spite of thestructurally increased stiffness, can satisfy the above mentionedconditions. It is an essential feature of the product of the inventionthat there are flutes in two different plies, with the flute directionscriss-crossing to give all directions of the laminate increasedstiffness or resilience.

More precisely the product of this aspect of the invention is specifiedin a laminate comprising a monofilm-formed or multifilm-formed ply (A)and another monofilm-formed or multifilm-formed ply (B) both mainlyconsisting of orientable thermoplastic polymer material, in which A hasa fluted configuration and B on a first side is adhesively bonded inbonding zones to the crests on a first side of A, characterized in thata) B also has a fluted configuration, the flute direction of B formingan angle from generally about 30° up to and including 90° to the flutedirection of A and the said bonding zones being on the crests of thefirst side of B to produce spot bonding with the crests on the firstside of A, b) the adhesive bonding is i) directly A to B and establishedthrough a lamination layer ‘on A and/or B; ii) established through aseparate thin bonding film; or iii) through a fibrous web adapted forbonding, and c) the wavelengths of the flutes in A and/or B are nolonger than 5 mm, and the wavelengths of the flutes in both A and B areless than 10 mm. Preferably the wavelengths of the flutes in each of theplies are no more than 5 mm.

While I have identified the laminate as comprising the plies A and B,each ply can consist of-one or more films, normally extruded films, andeach extruded film can and normally will consist of several coextrudedlayers.

In itself the application of the corrugated paperboard principle tothermoplastic film material is not new, but in the prior art this isdone by laminating a fluted film to a flat film. Furthermore the finestflute structure which has been disclosed in patent literature, namely inUS-A-4132581 col. 6, In. 66 is 50+/−3 flutes per foot corresponding to awavelength of about 6.0 mm. It is very doubtful that a wavelength lowerthan this can be achieved by the method disclosed in this patent, inwhich the first bonding process takes place by the use of a row of manysealer bars supported and transported by a belt. The sealer bars aretransverse to the direction of movement (the machine direction) so thefluting also becomes perpendicular to this direction. The use of themethod is stated to be manufacture of board material, and the thicknessof the fluted ply is indicated to be about 0.004-0.025 inches (0.10-0.625 mm). In the example it is 0.018 inches (0.45 mm).

Other patents dealing with the use of the corrugated paperboardprinciple to thermoplastic film for the making of panels or boards areUS-A-3682736, US-A-3833440, US-A-3837973, EP-A-0325780 andWO-A-94/05498.

JP-A-02-052732 discloses laminates consisting of a corrugatedthermoplastic film bonded to a flat thermoplastic film, which on itsother side is bonded to paper. The paper and flat sheet are first joinedand then the corrugated film is added. The flutes, which also in thiscase are perpendicular to the machine direction, are pressed flat andadhesively closed at intervals so that a large number of airtightvesicles are formed. The stated use of this product is for cushionmaterial, sound-insulating material, heat- and moisture-insulatingmaterial and wall decorative material. The thicknesses of the corrugatedsheet and flat sheet are not indicated, neither are the wavelength ofthe fluting and the length of the vesicles.

The inventor of the present invention has found that specialconstructions of the corrugator/laminator generally is needed in orderto make the miniflutes, since if the pitch is low on the gear rollerswhich produce the fluting and the lamination, the corrugated film willtend to jump out of the grooves in the forming and laminating rollerduring its passage from the location where the forming of flutes takesplace to the location where the bonding takes place. In a conventionalcorrugator for manufacture of corrugated paperboard there are providedtracks or shields to hold the fluted paper in the grooves. At ambienttemperature this allows the paper to be more readily permanently formed.Similar tracks or shields in unmodified form cannot be used withthermoplastic film under production conditions since friction againstthe track or shield quickly would create congestion by heating of thepolymer.

An improved, frictionless way of holding of flutes of paper in thegrooves of a roller is known from US-A-6139938, namely by maintaining acontrolled under pressure within the grooves (see FIGS. 9 and 10 andcol. 7 lines 25-34). This US patent deals entirely with corrugated paperlaminates .having particularly low wavelength, while manufacture ofcorrugated structures from thermoplastic films is not mentioned.However, the improved method of holding the flutes will in fact also,depending on the film thickness, be applicable to' fine flutes inthermoplastic film .. This was implemented in connection with thedevelopment of the present invention.

The present development of the particularly fine flute structure can beexpected to make the corrugated paperboard principle applicable tocompletely different fields of use such as the fields mentioned at thevery beginning of this specification.

This has comprised a development of new types of machinery based ongrooved rollers with a very fine pitch. As it will appear from example 1the wavelength in each ply of a 90 gm⁻² minifluted 2-ply laminate has inactual fact been brought down to 1.0 mm through a process which can becarried out industrially. Especially by use of after-shrinkage it canprobably be brought further down e.g. to about 0.5 mm. The mentioned 90gm⁻² gauge corresponds to an average thickness of about 0.096 mm if thelaminate were pressed flat with equal thickness all over.

The invention is not limited to gauges corresponding to pressed-flatthicknesses around this value, but also comprises, very generallyspeaking, minifluted laminates of an average thickness in compacted formwhich is roughly about 0.3 mm or lower. Thicknesses down to about 0.03mm or even lower can be made for special purposes, such as for instancebacksheets on napkins (diapers).

Nor is the invention limited to the use in connection with crosslaminates of oriented films. For different purposes differentcombinations of strength properties are required. Crosslaminates can, asis known, be produced with suitable combinations of several categoriesof strength properties but for many purposes other types of strengthlaminates may be preferable when the cost of the manufacturing processalso is considered, and the present invention can also be useful in suchother strength laminates as further specified below.

By making the wavelength as low as about 5 mm or less, the laminateloses—gradually with the reduction of wavelength -, its character ofbeing a board material and develops the appearance, handle and bendingproperties of a resilient flexible film. It also gets improved punctureand tear properties, relative to its weight. Compared to non-corrugatedlaminates of the same composition and same square weight it feels muchmore substantial due to the increased stiffness and resilience in alldirections and due to the increased volume.

In the case of crosslaminates it is well known that a weak bondingbetween the plies, or strong spot-bonding or line-bonding, gives veryimproved tear propagation resistance, since it allows the tear toproceed in different directions in the different plies. Thereby thenotch effect is reduced. Since a crosslaminate with both pliescorrugated will be spot-bonded, it will show improved tear propagationresistance, no matter whether the wavelength is short or long, butminifluting makes the tear stop after a very short propagation, which ofcourse is very advantageous in most cases. However, the improvements intear propagation resistance, is a result not only of the spot-bonding,but also of the fluted form of each ply, which gives the ply betterpossibilities of changing orientation or fibrillating during thetearing, thereby absorbing energy. This is a kind of buffer effect.

When laminates according to the present invention are used for textileor textile-like application there is the additional advantage that thestructure with crisscrossing miniflutes, due to a smoothing influencewhen the laminate is given creases, reduces the rustle, or makes thetone of rustle deeper. This adds to the impression that the laminate isa kind of textile. This feature has special importance in applicationsas a garment for people or animals, e.g: weather protective or gasprotective garments, then rustle is felt irritating and disadvantageousin some uses. It should hereby be mentioned that crosslaminatesaC90rding to the inventor's earlier patents, with a barrier layerincluded, has found application in several countries for gas protectivegarments, but due to the rustle did not succeed against competition. Itis believed that this problem will be fully solved by use of the presentinvention.

It is also found that the special structure comprising fluted, mutuallyspot bonded plies, with the flutes criss-crossing,. provides thelaminate with some diagonal give like that of woven fabrics, althoughless than in woven fabrics, and very dependent on the depth of theflutes and of the coefficient of elasticity (E). This property enhancesthe ability of the laminate to fit with objects which it covers orencases. Heat insulating properties due to the miniflutes also help togive the laminate a textile-like character.

The inventor of the present invention has also filed an earlier,simultaneously pending WO-A-02-02S92 which was not published on thefirst priority date of the present invention. The two inventions areclosely related, however the product claims of the earlier applicationconcern a laminate of which a minifluted ply is laminated on one or bothsurfaces to a non-fluted (flat) ply, or a non-fluted (flat) ply islaminated on one or both surfaces to a “minifluted” ply. Contrary tothis, it should be emphasized that in the present invention two flutedplies with different direction of the flutes are directly bondedtogether crests to crests, for instance through a 2 5 lamination layer.Thus the structure of the old invention can be considered like amultitude of fine pipes bonded together, while the spotbonded structureof the present invention has a more flexible but resilient character. Itallows a deeper bending without causing permanent deformations, and isalso the reason for the above mentioned tendency to some textile-likediagonal give.

If two laminates according to the old invention, each consisting of oneminifluted ply and one flat ply, are bonded together flat ply to flatply, with the two directions of flutes perpendicular to each other, theresultant 4-ply will not exhibit properties like those of the presentinvention, since the two fluted plies are not directly bonded togetherin a spotbonded arrangement crests to crests. The flat in-between plyworks against flexibility and resilience.

In the present invention the direct bonding crests to crests through alamination layer will normally best be effected through a lower meltingsurface layer on at least one of the plies, formed in a coextrusionprocess. However, as stated in the claims, it is also possible to use aseparate thin bonding film. This is preferably done by extrusionlamination, which will not harm the above mentioned textile-likebehaviors, provided the lamination layer extruded in such procedure isso thin that it does not essentially influence the diagonal give,flexibility and resilience of the laminate. The use of a fibrous webadapted for the bonding can also be suitable.

For the sake of good order, it should be mentioned that there alreadyhave been described minifluted laminates in literature, however thesedisclosures concern laminates of which the fluted ply consists of amaterial which is not a thermoplastic film nor an assembly ofthermoplastic films, and apart from this the inventor has not found anydisclosure of two fluted plies in criss-crossing arrangement, neitherconsisting of thermoplastic nor of any other material.

US-A-6139938, which has been mentioned above has for its object a 3-plypaper laminate with a corrugated paper sheet in the middle and flatpaper sheets on each side, like normal corrugated paper board, howeverclaimed to comprise 500-600 flutes per meter corresponding to awavelength of 1.67-2.00 mm. The stated purpose is to improve theprintability.

JP-A-07-251004 relates to an absorbing product in which a planethermoplastic synthetic fibre sheet is thermally bonded to a corrugatedsheet mainly consisting of active carbon fibres fibers. The wavelengthof the corrugation is 2.5-20 mm.

JP-A-08-299385 relates to an absorbent laminate consisting of a flutednon-woven fabric bonded o,! one side to a plane sheet or film, which canbe a thermoplastic film. Between these two plies is nested a waterabsorbing material. The wavelength is claimed to be 3-50 mm, and it isstated that there would not be sufficient space for the absorbingmaterial if it were less. The product is for diapers and similarproducts.

The method of making the present corrugated laminate of twomonofilm-formed or multifilm-formed plies is defined in a method ofmanufacturing a laminate of a first monofilm-formed or multifilm-formedply with a second monofilm-formed or multifilm-formed ply both mainlyconsisting of orientable thermoplastic polymer material, in which thefirst ply has a waved flute configuration, and, the second ply on afirst side is adhesively bonded in bonding zones to the crests on afirst side of A, in which further the waved flute structure of the firstply is formed by the use of a grooved roller, and the said bonding withthe second ply is carried out under heat and pressure and also under useof a grooved roller, characterized in that a) the second ply also isgiven a waved configuration, whereby under use of at least one groovedroller the flute direction of the second ply is made at an angle to theflute direction of the first ply and the said bonding zones areestablished on the crests of the first side of the second ply tointroduce spot bonding with the crests on the first side of the firstply, b) the adhesive bonding I) is directly first to second ply andestablished through a lamination layer on at least one of these plies;ii) established through a separate thin bonding film; or iii)established through a fibrous web adapted to the bonding; and c) thewavelengths of the flutes in both plies are no longer than 10 mm, andthe wavelengths of the flutes in at least one of the plies are no longerthan 5 mm. Preferably the main direction in which the flutes of one ofthe plies extends is generally substantially perpendicular to the maindirection in which the flutes of the other ply extends. As it willappear from explanations below, the flutes are not always strictlyrectilinear, and therefore the expression “main direction” is used.Preferably one of the flute directions essentially coincide with themachine direction of the lamination.

Thus the waved flute structure in one of the plies can be establishedessentially in the machine direction in a generally transverseorientation process by taking the ply before lamination through a set ofdriven mutually intermeshing grooved rollers, whereby the grooves on therollers are circular or helical and form an angle of at least 60° withthe roller axis.

In this procedure the ply may be passed directly from its exit from oneof the grooved stretching rollers which flute the ply to the groovedlamination roller, while these two grooved rollers are in closeproximity to each other, have grooves of the same pitch when measured atthe respective operational temperature, and are mutually adjusted in theaxial direction. A preferable modification of this routing, namely theintroduction of “attenuated zones”, is mentioned below.

In another procedure the fluted structure in one of the plies can beestablished essentially perpendicularly to the machine direction bymeans of rollers in which the grooves are essentially parallel with theroller axis, as normal when making corrugated paper board. The twoprocedures are conveniently combined, so that before the lamination oneply is supplied with essentially longitudinal flutes, and the other plyis supplied with essentially transverse flutes, and the laminationrollers are supplied with grooves, one with the grooves essentially inthe machine direction, the other with its grooves essentiallyperpendicular to this, and the procedure is adapted so that thepreformed generally longitudinal flutes will fit into the generallylongitudinal grooves in one lamination roller, while the preformedtransverse flutes will fit into the transverse grooves in the otherlamination roller. One of the lamination rollers should normally be arubber roller. After the lamination the flutes in one or each ply can bemade deeper by shrinkage of the other ply in the appropriate direction.This of course depends on orientation in at least one of the pliesgenerally in the same direction as the direction of its flutes.

In a simplified procedure, which however generally makes the flutes inone of the plies more shallow, only one ply is supplied with flutesprior to the lamination. Both lamination rollers normally have grooves(but some exceptions will be mentioned later), one roller made so thatthe preformed flutes in one ply will fit into its grooves, and the othermade so that its grooves are generally perpendicular to this direction.Thus the laminate becomes spot-bonded, and when the fluted plysubsequently is caused to shrink along the direction of its flutes(which depends on the ply having orientation in this direction) the flatply will buckle up, forming flutes generally perpendicular to thepreformed flute. As mentioned above usually this will produce relativelyshallow flutes in the originally flat ply.

While the angle between the flutes in ply A and the flutes in ply Bshould be generally about 30° or more, it is better to make it generallyabout 60° or more, and usually best to make it generally about 90°.

Suitable dimensions in the laminate and divisions on the laminatingrollers are stated in the product laminates are characterized in thatthe flute wavelength in each of the two plies is no more than 4 mm,preferably no more than 3 mm and still more preferably no more than 2mm; characterized in that in each of the two plies the curved length ofa flute is on average at least 5% and preferably at least 10% longerthan the linear wavelength, the curved length being understood as thelength of a curve through the cross section of a full flute waveincluding the bonding zone which curve lies in the middle between thetwo surfaces of the ply; characterized in that in at least one of saidplies the said average is at least 15%; characterized in that the widthof each bonding zone in at least one of the two plies is no less than15%, preferably no less than 20%, and still more preferably no less than30% of the flute wavelength and in a method characterized in that the'pitch of the grooved roller, which produces the lamination on the crestsis at the highest 3.0 mm, preferably no more than 2.0 mm and still morepreferably no more than 1.5 mm and in an apparatus in which the land onthe crest of the or each grooved laminating roller is at least 15%,preferably at least 20%, more preferably at least 30% of the pitch ofthe grooved of that roller; comprises a grooved roller for fluting afirst ply of thermoplastic polymer material, a grooved roller forfluting a second ply of thermoplastic polymer material, means fordirecting the first and second plies from their respective groovedrollers between a set of laminating devices with the plies arranged inface to face contact with one another and with the flutes of the firstply generally directed at an angle to the flutes of the second ply, theset of laminating devices, comprising, on the side facing the secondply, a heated porous bar and on the side facing the first ply, anopposite laminating device, wherein said porous bar is adapted toproduce a film of hot air to press the plies towards the oppositelaminating device and bond the plies together at the crests of theflutes of the second 10 ply to form a laminate, and the oppositelaminating device is a roller or a porous bar, the grooved flutingrollers having groove pitches such that in the laminate the plies eachhave flutes of wavelength less than 10 mm and the flutes of at least oneof the plies have a wavelength no longer than 5 mm. Cross-sectionaldimensions are measured on micrographs.

With reference to FIGS. 15 and 16, the lengths, in a laminatecharacterized in that in each of the two plies the curved length of aflute is on average at least 5% and preferably at least 10% longer thanthe linear wavelength, the curved length being understood as the lengthof a curve through the cross section of a full flute wave including thebonding zone which curve lies in the middle between the two surfaces ofthe ply, are distances from X to Z one following the curved routethrough the middle of A, the other the direct, linear route.

For the textile-like applications the flute wavelength should preferablybe as low as practically possible in both plies, having hereby alsoregard to the economy of the manufacturing process, this means generallyabout 1-1.5 mm, while for applications in stiff products like smallboxes or self standing pouches, it should preferably be similarly low onthe side which is the outside in the final product, and which possiblymust be printed, but should preferably be higher on the side which isthe inside in the final product. When the flute wavelength is about 1mm, the quality of print can be reasonably good.

The fluted plies should normally consist of material which is orientableat room temperature and then suitable polymers are polyolefins. However,there are cases in which there is no special advantage in suchproperties, thus e.g. polystyrene will be suitable for stiff sheetmaterial applicable for conversion to small boxes or selfstandingpouches if there is little need for high strength.

At least one of the plies may comprise a barrier film, e.g. forprotection against oxygen or, as already mentioned, against harmfulsubstances, such as gaseous substances.

When flutes are formed by means of grooved rollers prior to thelamination they will become evenly formed and extend in a generallyrectilinear fashion. However, when the grooves are formed entirely byshrinkage after the lamination, their shape will be determined by thepattern of grooves in the lamination roller contacting the flat ply andthe degree of shrinkage of the shrinkable ply. This can of course alsobe an even rectilinear pattern, but in order to obtain aesthetic orinteresting visual effects, the pattern of the flutes in this ply can bedifferent. Thus although the flutes must extend mainly along thedirection which is generally perpendicular to the flute direction in theother ply, they can nevertheless be made curved or zig-zagging and/orbranched by an appropriate shaping of the pattern of grooves in thelamination roller (normally a rubber roller) which this ply contacts, orthey can be made differently shaped in a pattern which gives a visualeffect showing a name, text, logo or similar. Such patterns in thelamination roller can be made by methods known from rubber stereography.

For the sake of completeness it should also be mentioned that waved,partly branching and partly interrupted flutes in one ply also can beformed spontaneously and at random under use of a smooth laminationroller, namely when the bonding strength is suitably adjusted to allowpartial delamination during shrinkage of the other ply. Such surfacestructure looks like naturally wrinkled skin or leather. There can alsobe achieved interesting visual effects by making, a part of thementioned lamination roller smooth and a part supplied with grooves, ina suitable pattern. The above mentioned marking, showing a name, text,logo or similar can for instance be made in this way.

Such interesting visual effects and/or appearance of the laminate astextile-like, can be enhanced when at least one of the two plies has ametallic or iridescent gloss or where the two plies are given differentcolors.

For most applications it is highly preferable that either the thicknessof each of the said plies is generally the same in bonded and unbondedzones, or at least one ply exhibits solid-state attenuated zones, in thefollowing referred to as the “first” such zones, formed by a so-called“segmental stretching”, and extending parallel to the flute direction,each bonding zone mainly being located within such a first attenuatedzone. Herein each first attenuated zone is understood as delimited bythe positions where the thickness is an average between the minimumthickness of this ply within the first attenuated zone and the ply'smaximum thickness within the adjacent non-bonded zone. The method ofmaking the fluted laminate with such first solid-state attenuated zoneslocated as mentioned requires a strict coordination between stretchingrollers and lamination rollers, and is specified: as a methodcharacterized in that prior to the said bonding process at least one ofsaid plies is solid-state stretched in narrow zones to form firstattenuated zones which are parallel to the selected direction of flutingin the ply, said stretching being generally perpendicular to the saiddirection and carried out between a set of grooved rollers bothdifferent from the grooved roller for lamination, and that the groovedroller for lamination is coordinated with the said set of groovedrollers for stretching in such a way that each zone of bonding mainlybecomes located within a first attenuated zone; as a methodcharacterized in that a suitably distinct stripe formation of the firstattenuated zone is established at least in part by giving the crests onthe grooved stretching roller intended to produce the stripes atemperature which is higher than the temperature on the crests on theother grooved stretching roller and/or by giving the crests on thegrooved stretching roller intended to produce the stripes a radius ofcurvature which is smaller than the radius of curvature of the crests onthe matching grooved stretching roller; as an apparatus comprising afirst set of grooved stretching rollers upstream from the laminatingstation for at least one of the plies, which stretches the material ofthe respective ply in a solid state and in a direction generallyperpendicular to the flutes to form first attenuated zones, wherein thegrooved stretching rollers, grooved fluting rollers and groovedlaminating rollers are coordinated so that the first attenuated zonesbecome the crests of the flutes and the bonding zones are mainly locatedwithin first attenuated zones; as an apparatus in which the last of thegrooved stretching rollers is in close proximity to the groovedlaminating roller and the grooves of each are of the same pitch at theoperating temperature of the apparatus and being aligned; and as anapparatus which comprises one or a series of heated grooved transferrollers located between the last of the grooved stretching rollers andthe grooved laminating roller, adjacent rollers being close together,the grooves of the stretching, transfer and laminating rollers havingthe same pitch at the operating temperature of the apparatus and beingaligned with one another.

In this connection, an esse'ltial attenuation of a ply in the non-bondedzones, as compared to the thickness in the bonded zones, will of coursehave a negative influence on the resistance to bending and theresilience, but It is generally easier to make the fluted laminate so.By contrast this resistance to bending is enhanced in comparison withthe situation when the thickness is even, when there are attenuatedzones and each bonding zone mainly falls within one of these attenuatedzones. The attenuated zones in at least one of the plies also facilitatethe manufacturing process as it later shall be explained. It is notedthat while attenuation by stretching in solid molten state reduces thetensile strength, attenuation by stretching in the solid state canincrease the tensile streng,th in the direction in which the stretchinghas taken place.

The first attenuated zones are shown as (6) in FIGS. 15 and 16. They arehere shown as almost exactly coinciding with the zones of bonding in thesections shown, which are sections drawn through the bonded spots.However, they need not be coincident like this, since the requirementonly is that each bonding zone mainly is located within a firstsolid-state attenuated zone. Thus, the bonding zones can to some degreeextend beyond the first attenuated zones, or the latter can extendbeyond the former. Preferable choices of relative zone widths for thelast case are specified as a laminate in which first attenuated zonesare present in at least one of the plies and in which the bonding zonesare generally coincident with the first attenuated zones.

Of course such extension of the first attenuated zones into non-bondedzones will reduce the stiffness, but will normally not reduce theresilience. It may even increase this property and will add to thetextile-like character. It can with a suitable choice of otherconditions, also provide the laminate with a higher tear propagationresistance and higher impact strength.

When at least one of the plies exhibits solid-state attenuated zones,the first attenuated zones of the ply are preferably attenuated to suchextent that the minimum thickness in such zone is less thah 75% of themaximum thickness of the ply in the non-bonded zone, preferably lessthan 50% and more preferably less than 30% of that maximum thickness.

A suitable method of achieving almost precise correspondence of thefirst attenuated zones with the bonding zones, at least in one ply, isto adjust the roller temperatures to the thickness of the attenuatedzones, at least in on ply, is to adjust the roller temperatures to thethickness of the attenuated zones and to the velocity of the plies, insuch a way thaUhese zones reach a temperature which makes them laminateadequately to the other ply, while the film material outside the zonesdue to its thickness does not reach a sufficient temperature. Acondition is that the flat crests on the grooved lamination roller arewider than and extend beyond each of the “first attenuated zones”. Thisis defined: as a laminate in which first attenuated zones are present inat least one of the plies and in which the bonding zones are generallycoincident with the first attenuated zones; a method in which thelamination layer is heated to the lamination temperature by heating fromthe opposite side of the ply, and in which the temperature of thelaminating roller and the thickness of the film in the first attenuatedzones is such as to allow the laminating layer to reach said laminationtemperature whilst the thickness of the ply outside the attenuated zonewhich is in contact with the crests of the grooved lamination roller issuch that the lamination layer outside the attenuated zone does notreach said lamination temperature, where the first attenuated zones andthe bonding zones become generally coincident; and as an apparatus inwhich the crests of the grooves of the laminating roller are wider thanthe first attenuated zone and in which the side of the ply opposite tothe face in contact with the other ply is heated in the laminationstation, preferably by supplying heat to the interior of the groovedlaminating roller.

A similar effect can find particular use when transverse flutes in a plywill be formed by shrinkage of the other ply, as explained in connectionwith FIGS. 17 and 18. In such case the lamination roller which directlycontacts the first mentioned ply, needs not be supplied with grooves butmay be smooth, provided the ply has been supplied with first attenuatedzones and the process conditions are adjusted so that the bonding onlytakes place in these zones. See further at the end of description toFIGS. 17 and 18.

With reference to FIGS. 18 and 19, the first attenuated zones are formedon and at the tips of roller 8 by the transverse stretching produced bythe intermeshing between this roller and roller 7. If the surface shapeof roller 8 or other process parameters are not properly adapted to thecomposition and state of the ply which is being stretched, thisstretching may come out as a twin zone with unstretched or lessstretched material between the stretched tracks. In such cases eachfirst attenuated zone should, in the understanding of the claims beconsidered as comprising the total of both twin zones and theunstretched or less stretched track between them.

In addition to first attenuated zones in at least one of the two plies,such ply can be supplied with a further set of solid-state attenuatedzones, hereafter referred to as the second such zones. They are locatedbetween each pair of adjacent first attenuated zones, are narrower thansaid first attenuated zones and are placed on the non-bonded crests ofthe respectively ply. This is illustrated in FIG. 16. The method ofmanufacturing these second attenuated zones is specified as a methodcharacterized in that prior to or after the formation of the firstattenuated zones, another set of grooved rollers produces secondattenuated zones which are another series of solid state oriented narrowzones in the same ply, parallel with the first attenuated zones andnarrower than the latter, while the grooved rollers which produce 20said second attenuated zone are coordinated with the grooved rollerswhich produce the first attenuated zones so that each second attenuatedzone becomes located generally in the middle between two neighboringfirst attenuated zones and as apparatus comprising, between the saidgrooved stretching rollers and the laminating station, a second set ofgrooved stretching rollers, which stretches the material of the saidrespectively in a solid state and in a direction generally perpendicularto the flutes to form second attenuated zones extending parallel to andbetween said first attenuated zones which are narrower than said firstattenuated zones, whereby the second attenuated zones become the troughsof the flutes.

The second attenuated zones act as “hinges”, and if they are made narrowand deep enough they improve the stiffness, since the cross-section of Abecomes zig-zagging instead of smoothly waved (as described further inconnection with FIG. 16) and A and B thereby get triangular crosssections. The second attenuated zones can also in some cases facilitatethe manufacturing process, as it is explained below.

In addition to the improvements in stiffness and resilience caused bythe first and second attenuated zones (improvements seen in relation tothe average thickness of A) each set of zones also in many casesimproves the resistance against shock action, such as impact strength,shock-puncture resistance and shock-tear propagation resistance. This isbecause there is started a stretching in the ply transverse to theflutes, and this stretching often has a tendency to progress under shockaction, whereby the first and second attenuated zones can act asshock-absorbers.

The proper location of thefirst attenuated zones relative to the zonesof bonding can be established by suitably coordinating the groovedstretching rollers which make the “first attenuated zones”, with thegrooved rollers for lamination.

The second attenuated zone which have been described above, can beformed by stretching between a further set of grooved rollers suitablycoordinated with the grooved rollers which produce the first attenuatedzones.

The advantages of the first and second attenuated zones in terms ofproduct properties have already been explained. An advantage in terms ofprocess features is that the first attenuated zones allow increases ofvelocity and therefore improved economy, since the zones in ply A whichare going to be bonded, have been made thinner and therefore requireless heating time during the application of heat prior to the bonding.Furthermore the first attenuated zones and in particular the combinationof first and second attenuated zones can be of great help for theprocess by acting as hinges in ply A. In the type of apparatus in whichthe grooved roller for lamination has grooves which are generallyparallel with its axis, these hinges make it possible to direct evenrelatively heavy A-ply into fine grooves. In the type of apparatus inwhich the grooves are circular or helical, but in any case approximatelyperpendicular to the roller axis, the hinges help to keep ply A in trackduring its passage from grooved roller to grooved roller, in other wordsthe hinges help to coordinate the action of the grooved laminationroller with the action of the preceding set or sets of grooved rollerswhich form the flute under a simultaneous transverse stretching.

Preferable ways of coordinating and carrying out the different groovedroller operations are further specified: as methods characterized inthat this ply is passed from its exit from the last of the grooved andfluting rollers to the grooved lamination roller over one or a series ofheated, grooved transfer rollers, the grooved rollers in the rowstarting with the grooved stretching rollers and ending with the groovedlamination roller each being in close proximity to its neighbor orneighbors, whereby each of the grooved rollers in the row has the samepitch when measured at their respective operational temperature, andbeing mutually adjusted in the axial direction for alignment of thegrooves; characterized in that each grooved roller used to form theflutes in one of the plies and each grooved roller used to form thefirst attenuated zones in this ply if such zones are produced, and eachgrooved roller used to form the second attenuated zones if such zonesare formed in this ply and a grooved roller which the ply follows beforeand during the lamination if such roller is used, are rollers in whichthe grooves are essentially parallel with the roller axis, and means areprovided to hold the flutes of the said ply in the respective groovesduring the passage from the position where the flutes are formed to theposition where lamination takes place, said holding means adapted toavoid a frictional rubbing on the ply during said passage; characterizedin that the flutes in this ply are formed by use of an air jet or atransverse row of air jets which directs A into the 'grooves on theforming roller; characterized in that first attenuated zones are formedby grooved rollers acting in coordination with the grooved roller usedfor lamination, and said coordination consists in an automatic fineregulation of the relative velocities between the rollers; andcharacterized in that said second attenuated zones are formed by groovedrollers acting in coordination with the grooved rollers used to producethe first attenuated zones, and said coordination consists in anautomatic fine regulation, of the relative velocities between therollers and as apparatuses: in which the last of the grooved stretchingrollers is in close proximity to the grooved laminating roller and thegrooves of each are of the same pitch at the operating temperature ofthe apparatus and being aligned; comprising one or a series of heatedgrooved transfer rollers located between the last of the groovedstretching rollers and the grooved laminating roller, adjacent rollersbeing close together, the grooves of the stretching, transfer andlaminating rollers having the same pitch at the operating temperature ofthe apparatus and being aligned with one another; in which the groovedfluting roller for one of the plies has the grooves arrangedsubstantially parallel with the roller axis and in which substantiallyfrictionless holding means are provided for holding the flutes of therespective ply in the grooves; and in which the frictionless holdingmeans comprises air pressure difference between opposite sides of theply at the groove.

The films used for each of the plies are usually but not always (as itappears from the foregoing) prior to forming of the waved configurationsand prior to making of the first and second attenuated zones (if suchzones are made), supplied with orientation in one or both directions,the resultant main direction of orientation in each ply being generallyin the direction which is selected to become the direction of fluting.This can be by means of a strong melt orientation, or preferably,alternatively or additionally by known stretching procedures carried outin the solid state. If the process is adapted to make the flutesgenerally parallel with the machine direction, this will be a generallylongitudinal orientation process, which is simple, and if the process isadapted to make the flutes generally perpendicular to the machinedirection, it will be a generally transverse orientation process whichis much more complicated to establish, and usually requires expensivemachinery but is well-known.

More precisely expressed one or both plies will normally, outside theirfirst attenuated zones if such zones are present, be molecularlyoriented mainly in a direction parallel to the direction of their flutesor in a direction close to the latter. (The main dire,ction oforientation can be found by shrinkage tests).

Thus, in the judgement of the inventor, the product of the invention inits most important embodiment is a crosslaminate with the main directionof orientation in each ply generally coinciding with the direction ofits flutes. If one or both plies are composed of several films, the saidorientation mainly in a direction parallel to the direction of theflutes, should be understood as the resultant of the different monoaxialor biaxial orientations in the said films, which may be differentlydirected.

As an example, ply A may consist of a single coextruded film withorientation and flutes extending in the machine direction, while ply B,the flutes of which extend perpendicular to the machine direction initself is a crosslaminate of two films, each oriented at an anglesubstantially higher than 45° (e.g. one +60° and the other −60°) to themachine direction. Each of these obliquely oriented films can beproduced by helical cutting of a longitudinally oriented tubular filmsas described e.g. in EP-A-0624126 and GB-A-1526722, both mentionedabove, and disclosed in more detail in EPA-0426702. The lastspecification also discloses a method of obtaining a uniaxial orstrongly unbalanced melt orientation which is perpendicular to themachine direction, namely by twisting of a tubular film coming out ofthe extrusion die followed by helical cutting under the calculatedangle.

The ply which in itself is a crosslaminate, should preferably be made asa laminate prior to the flute producing process step, preferably alamination through lower melting, coextruded surface layers.

Similarly ply A, instead of being a single coextruded longitudinallyoriented film, may in itself be a crosslaminate of two films, eachoriented at an angle substantially lower than 45° (e.g. one +30° and theother −30°) to the main direction, and each produced by helical cutting.These two films may after their joining be further stretched in thedirection which then is . machine direction. Of course this is morecomplicated than simply using one coextruded longitudinally orientedfilm as ply A, but it can provide essential improvements in tear andpuncture strength.

A very surprising property of the laminate according to the invention isan improved heatseal strength when the seal is tested by peeling (asopposed to shear testing of a seal) especially when shock tested so.Provided the boundary of the seal is made with a pronouncedly smoothsealer bar as normal in heatsealing, instead of a sharpedged sealer bar,a result of the flute form is that there are shaped out fine and even“pockets” at the boundary of the seal, which “pockets” are found to givea very pronounced shock absorbing effect, protecting the seal duringshock peeling.

While the use of the present invention mainly is for strength film, thisneeds not always mean high strength in all directions. By contrast thereare cases, e.g. in construction of bags, where the focus should be onthe strength in one direction, combined with a certain puncture and tearpropagation resistance. As an example a conventional industrial bag offilm thickness 0.160 mm made from a blend of 90% LDPE and 10% LLDPE willtypically in its longitudinal direction show a yield force of 20 Ncm⁻¹,i.e. a yield tension of 12.5 MPa and in its transverse direction shows ayield force of 16 Ncm⁻¹, i.e. a yield tension of 10.0 MPa.

Commercially available crosslaminated film material in average thickness0.086 mm for heatsealable bags developed by the inventor andmanufactured in accordance with the above mentioned EP-A-0624126 showsin its strongest direction a yield force of 20 Ncm⁻¹, i.e. 23 MPa, andin its weakest direction a yield force of 17 Ncm⁻¹, i.e. a yield tensionof 20 MPa.

Since the invention in principle relates to flexible laminates for useswhere relatively high strength is required, although the emphasis of theinvention is on stiffness, feel and appearance, the yield tension of thelaminate in its strongest direction should normally be no less than 15Mpa, preferably no less than 25 MPa. Correspondingly the ultimatetensile tension is conveniently about twice the said indicated values,or more. Here the cross section in mm2 is based on the solid materialonly, not including the air spaces, and it is an average, consideringthat ply A may have attenuated zones. The yield tensions mentioned hererefer to tensile testing at an extension velocity of 500% per minute.They are established from strain/stress graphs. These graphs will beginlinear according to Hook's law, but will normally soon deviate fromlinearity although the deformation still is elastic. In principle theyield tension should be the tension at which the deformation becomespermanent, but this critica.1 value, which is velocity dependent, ispractically impossible to determine. The way yield tension is normallydetermined in practice, and also considered determined in connectionwith the present Claims is the following:

In case the tension reaches a relative maximum, then remains constant ordecreases under continued elongation, later to increase again untilbreak occurs, the relative maximum of the tension is considered to bethe yield tension. The sample may also break at this point, and then theyield tension equals the ultimate tensile tension. If however thetension continues to increase with the continued elongation, but withmuch lower increases in tension per percentage elongation, then thestrain/stress curve after yield, and after it practically has become astraight line, is extrapolated backward to intersect with the line whichrepresents the Hook's-Law-part of the stretching. The tension at theintersection between the two lines is the defined yield tension.

An embodiment of the invention is characterisation in that at least oneof the plies by the choice of polymer material or by an incorporatedfiller or by orientation, within the non-bonded zones exhibits anaverage yield tension parallel to the direction of fluting, which whenit is determined as explained above, if no less than 30 Nmm⁻²=30 MPa(cross section of ply A alone), preferably no less than 50 MPa and stillmore preferably no less than 75 MPa.

An example of a laminate construction which can be simpler inmanufacture than a crosslaminate, and still for many purposes can beconsidered a high strength laminate, is a laminate according to theinvention in which one ply, say A, is uniaxially or biaxially orientedin very unbalanced manner with the main direction of orientationgenerally coinciding with its direction of flutes (this may mainly bethe machine direction or mainly be perpendicular to the latter) whileply B, without exhibiting a main direction of orientation generallyperpendicular to that of A, is biaxially oriented so that theorientation outside its first attenuated zones (if such zones arepresent) anyway is higher than A's average orientation in the samedirection outside its first attenuated zones (if such zones arepresent). Ply B may simply be a strongly blown film.

In some cases there is advantage of having different elastic propertiesin different directions, and in such cases the materials may be chosenso that B has a lower coefficient of elasticity than A, both as measuredin the direction perpendicular to the flute direction of A.

In an interesting special case, e.g. for bags which shall withstand adrop from a great height, the choice of material for B and the depth ofA's. fluting is such that by stretching of the laminate perpendicular tothe direction of A's fluting up to the point where A's waving hasdisappeared, B still has not undergone any significant plasticdeformation, preferably B is selected as a thermoplastic elastomer. A isalso in this case oriented in a direction parallel to the flutes orclose hereto (orientation in first attenuated zones is disregarded).

As it appears especially from the introduction, the present invention isexpected to be applicable in several very different fields of uses, alsouses where stiffness is the most important requirement, for example theuse for stand-up pouches. A laminate characterized in that by the choiceof polymer material or by an incorporated filler or by orientation, thecoefficient of elasticity E in at least one of the plies, measured inthe unbonded zone of the ply in the direction parallel to the flute, asan average over the unbonded zone is no less than 700 MPa, andpreferably no less than 1000 MPa specifies the stiffness selected forsuch applications.

Some or all of the flute in one or both plies may be flattened atintervals, and then preferably bonded across each ones entire width atthe flattened locations to make the two arrays of flutes form closedpockets. The flattened portions of a number of mutually adjacent flutesor of all flutes should usually be in array. The flattening can serve aspreforming of a sharp bending in the final product“e.g. to help making astand-up pouch, or making the bent edges of a tarpaulin. The closedpockets may also be made for purposes of litheencapsulation/canalization aspect” of the present invention, which nowshall be described.

The encapsulation/canalization aspect comprises a number of embodimentswhich for different practical purposes utilize the interior cavities inthe laminate, optionally in combination with suitable perforations,either to canalize a flow of liquid or air, or to encapsulate fillingmaterial in particular, fibrous, filament or liquid form. The latter maye.g. be a preservative for goods packed in the flexible laminate. Thesedifferent embodiments and some of their applications appear fromproducts: characterized in that at least some of the channels formed bythe flutes in A and B, which channels may be closed to pockets, containa filling material in particulate, fibrous, filament or liquid form;characterized in that said material is a preservative for goods intendedto become packed in or protected by the laminate, preferably an oxygenscavenger or ethylene scavenger, a biocide, such as a fungicide orbactericide, a corrosion inhibitor or a fire extinguishing agent,optionally with micro-perforations established in the flutes to enhancethe effect of said preservative; characterized in that both A and B aresupplied with a multitude of perforations, whereby the perforations donot reach into the bonded spots, and the perforations in A are displacedfrom the perforations in B so as to cause gas or liquid when passingthrough the laminate, to run a distance through the flutes generallyparallel to the main surfaces of the laminate; the channels formed bythe flutes may be closed to form pockets; characterized in that thechannels or pockets contain filling material adapted to act as a filtermaterial by holding back suspended particles from a fluid passingthrough the channels or pockets or is an absorbent or ion-exchangercapable of absorbing or ion-exchanging matter dissolved in such fluid,said filler optionally being fibre-formed or yarn-formed; in which bychoice of hydrophobic properties of at least the inner surfaces of thechannels or pockets formed by the flutes and by selected small spacingof said channels or pockets, and choice of the distances between themutually displaced perforations in A and B, there is achieved adesirable balance between the pressure needed to allow water through thelaminate and the laminate's capability to allow air and vapor to passthere through; characterized by a nap of fibre-like film portionsprotruding from the borders of the perforations of at least on onesurface of the laminate; used as a sanitary backsheet, preferably on adiaper or as a sheet for covering a patient during surgery; used forinsulation of buildings; and used as a geotextile which allows water topass but holds fine particles back, methods of making these products:characterized in that particulate, liquid or fibre-or yarn-formedmaterial is filled into some at least of the channels formed by the twoarrays of flutes, this filling taking place prior to or during thelamination; characterized in that after filling the filled channels areclosed at intervals by pressure and heat to form filled pockets;characterized in that prior to, simultaneously with or following thefilling step perforations are made in the laminate at least on one sideto help the filling material or part thereof dissipate into thesurroundings or to allow air or liquid to pass through the fillingmaterial; characterized in that there is made a multitude ofperforations in the first and in the second ply, but limited to areas,where the two plies are not bonded together, and the perforations in thefirst ply being displaced from the perforations in the second ply toforce air or liquid which passes through the laminate to run a distancealong one or more channels; characterized in that in one process stepthere is melted a multitude of holes in the first but not in the secondply or in the second but not in the first ply, these holes being formedby contacting flutes of the first ply with protruding surface parts of ahot roller, which are moved at essentially the same velocity as thelaminate; characterized in that the holes are formed by contactingflutes of the second ply with protruding preferably sharp, surface partsof a hot roller, which are moved at essentially the same velocity as thelaminate, while heat insulating material prevents the flutes fromcontacting the hot surfaces of the roller, and preferably the laminateis pressed towards the protruding parts by means of air jets;characterized in that there is drawn a protruding nap of fibre-like filmportions out from the molten surroundings of the holes by blowing air inbetween the laminate and the hot roller, where the laminate leaves theroller and apparatuses: in which downstream of the grooved laminatingroller in the lamination station there is a flute flattening station inwhich at least some of the flutes in each ply are flattened and theplies bonded to one another under heat and pressure to form closedpockets; in which the flute flattening station comprises bars and/orcogs extending generally in the machine direction or the cross-directionand counter rollers, bars or cogs against which to bear; comprisingflute filling means for filling the flutes of one or both plies beforeor during the lamination station with particulate, fibre or liquidmaterial. The embodiment of the present invention in which the finecanals or pockets are used to entrap preservatives, have obviousadvantages over the usual method of blending such agents with thepolymers to be extruded into film form. One advantage is that theconcentration of the preservative can be much higher, another that thepreservative needs not be able to withstand the temperature ofextrusion. The preservative may reach the object to be preserved bymigration alone, or if the agent is solid it may gradually evaporate anddiffuse through sufficiently fine perforations or pores.

It is also customary to contain preservative agents in small bags whichare placed inside a package. Compared to this method of protection, thepresent invention has the advantage that the preservative agent can bedistributed almost homogeneously over the full area of the packingmaterial.

The filter material stated in a laminate characterized in that thechannels or pockets contain filling material adapted to act as a filtermaterial by holding back suspended particles from a fluid passingthrough the channels or pockets or is an absorbent or ion-exchangercapable of absorbing or ion-exchanging matter dissolved in such fluid,said filler optionally being fibre-formed or yarn-formed has manypotential uses, e.g. as a geotextile (a laminate used as a geotextilewhich allows water to pass but holds fine particles back) but also forinstance for water treatment in the chemical industry and in gas facemasks.

The laminate in which by choice of hydrophobic properties of at leastthe inner surfaces of the channels or pockets formed by the flutes andby selected small spacing of said channels or pockets, and choice of thedistances between the mutually displaced perforations in A and B, thereis achieved a desirable balance between the pressure needed to allowwater through the laminate and the laminate's capability to allow airand vapor to pass therethrough, which makes use of the capillary effectswithin the channels formed by the flutes, is an improvement over microporous film for similar purposes, since the balance between the waterstopping and air allowing effects can be optimized. The uses areespecially as backsheet e.g. on diapers, for moisture protection inbuilding constructions, and for “breathable” bags. However, for otherpurposes such as e.g. manufacture of a filter material for waterbasedsuspensions, there may contrarily be given hydrophilic properties to atleast the inner surfaces of the channels or pockets formed by theflutes. This can be achieved by the choice of the polymer material whichforms these surfaces, or by a surface treatment, e.g. by pressing orsucking corona-treated air from one surface to the other through thedescribed system of perforations and channels.

The hydrophobic properties e.g. of flutes made from polyolefin, maygradually decrease due to migration of apart-hydrophilic additive, e.g.an antistatic agent or a dispersive for pigments. When such additivescannot be avoided, this effect can be counteracted by adding smallamounts of a pronouncedly hydrophobic oil, e.g. paraffin oil, which alsocan migrate and “compete” with the hydrophilic substance.

The hydrophobic or hydrophilic properties of the channels formed betweenplies A and B, and/or the filtrating ability of the channel system, canbe enhanced by inserting in the laminate between A and B and bonded toboth, a fine fibrous web, e.g. a film with coextruded bonding layers onthe surfaces, which film before the lamination has been subjected tofibrillation by well-known means to achieve a fine fibre-network. Theweb can also advantageously be a fine web of melt-blown fibres, madefrom a lower melting polymer which can heatseal to both plies A and B.

The special way of making the perforations by melting, as described in amethod characterized in that in one process step there is melted amultitude of holes in the first but not in the second ply or in thesecond but not in the first ply, these holes being formed by contactingflutes of the first ply with protruding surface parts of a hot roller,which are moved at essentially the same velocity as the laminate and amethod characterized in that the holes are formed by contacting flutesof the second ply with protruding preferably sharp, surface parts of ahot roller, which are moved at essentially the same velocity as thelaminate, while heat insulating material prevents the flutes fromcontacting the hot surfaces of the roller, and preferably the laminateis pressed towards the protruding parts by means of air jets, is simpleand reliable to practice since the crests on the two surfaces of thelaminate are protruding so that the hot roller parts safely can formholes in one ply without harming the other ply. It is also a fastmethod. Further details appear from example 4.

As specified in a method characterized in that there is drawn aprotruding nap of fibre-like film portions out from the moltensurroundings of the holes by blowing air in between the laminate and thehot roller, where the laminate leaves the roller, the material which ismelted in the process of melt perforating can be dragged to form the napas a laminate characterized by a nap of fibre-like film portionsprotruding from the borders of the perforations of at least on onesurface of the laminate. In this case the surface contacting thenap-dragging hot roller must consist of a polymer material which stickssufficiently to the roller, e.g. it may consist of an ionomer/ethylenecopolymer. This can e.g. give a napkin or a sheet for covering a patientduring surgery a textile-like feel. Apparatus is defined as comprisingperforating means for cutting or melting holes into the flutes of one orboth plies in non-bonded zones; Apparatus defined in which theperforating means comprise a driven perforating roller having anarrangement of heated protrusions which contact and melt the material inthe flutes of the respective ply. Apparatus defined as furthercomprising pressurized air outlets for directing air at the ply whilethe material surrounding the perforations is molten. Apparatus definedin which the flutes of the ply are directed into contact with saidprotrusions by air jets directed at the surface of the ply opposite tothe perforating roller.

As an alternative to the perforating at elevated temperature, especiallyas this is described in example 4, the flutes in each ply can duringtheir formation be supplied with protruding “bosses” by use of a row oftips on some of the cogs which form the flutes, and the crests of theseprotruding “bosses” can continuously be llshaved” off after thelamination. Also in this way, holes going through both plies can beavoided.

The flutes of the laminate can also be used to give bags anti-slipproperties. When filled bags are placed in a stack, they are mainlyarranged so that each bag has its direction of length perpendicular tothe length of the bags immediately under it. To fit with this stackingarrangement, bags made from the laminate of the invention can withadvantage be constructed so that the flutes on one of its two majorsurfaces are generally perpendicular to those on the other majorsurface.

A further aspect of the invention, in which one or both of the plies isor are flat when fed to the laminating rollers is provided as a methodof manufacturing a laminate of a first ply with a second ply both mainlyconsisting of orientable thermoplastic polymer material and each havingone face comprising a lamination layer in which the first and secondplies are continuously fed in face to face relationship with thelamination layers in direct contact with one another between a pair oflaminating rollers between which heat and pressure is applied, wherebythe lamination layers become adhered to one another, in which the secondply is oriented mainly transversely of the machine direction, and isgenerally not shrinkable in solid state in the direction transverse toits orientation, and the first ply as it is fed to the laminationrollers is heat-shrinkable mainly in a shrink direction which isgenerally parallel with the machine direction, the lamination rollersapply heat and pressure in bonding zones arranged in continuous ordiscontinuous rectilinear lines extending in a direction which isgenerally perpendicular to said shrink direction, and after laminationthe first ply is caused to shrink in solid or semisolid state in thesaid shrink direction, whereby the second ply becomes fluted with flutesextending perpendicular to said shrink direction and having a wavelengthat the highest about 5 mm; as a method of manufacturing a laminate of afirst ply with a second ply both mainly consisting of orientablethermoplastic polymer material and each having one face comprising alamination layer in which the first and second plies are continuouslyfed in face to face relationship with the lamination layers in directcontact with one another between a set of laminating devices betweenwhich heat and pressure is applied, whereby the lamination layers becomeadhered to one another, in which the second ply is oriented mainlytransversely of the machine direction, and is generally not shrinkablein solid state in the direction transverse to its orientation, and isprior to the lamination rollers, segmentally stretched in its machinedirection to introduce first attenuated zones perpendicular to themachine direction, the first ply as it is fed to the lamination rollersis heat-shrinkable mainly in a shrink direction which is generallyparallel with the machine direction, the laminating devices comprise onthe side facing the second ply a heated flat roller or a heated porousbar adapted to produce a film of hot air to press the plies towards theopposite laminating device, which may be either a roller or a similarbar, the speed of the machine and the temperatures of the rollers beingadapted to heat the lamination layer in said first attenuated zones tothe lamination temperature, but not to heat the lamination layer in theadjacent non-attenuated zones to the lamination temperature, wherebybonding takes place only in the attenuated zones, and after laminationthe first ply is caused to shrink in solid or semisolid state in thesaid shrink direction, whereby the second ply becomes fluted with flutesextending perpendicular to said shrink direction and having awavelength- at the highest about 5 mm; as a method in which saidwavelength is at the highest about 3 mm; as a method in which the firstply is kept substantially flat throughout the manufacturing process; asa method in which the first ply is supplied with waves prior to thelamination, the wavelength being at the highest about 5 mm, preferablyat the highest about 3 mm, and the lamination zones are on the crests onone side of the waved first ply; as a method characterized in that, byuse of a take-off roller (13) of slightly waved surface, the laminate onits whole is supplied with a longitudinal waving to eliminate a tendencyto curling around its transverse direction; as a method in which saidrectilinear lines are discontinuous and in which the discontinuities inadjacent lines are aligned in the shrink direction. An example of thismethod is described below in Example 5.

Apparatus suitable for carrying out this method is a laminatingapparatus comprising a grooved roller for fluting a first ply ofheat-shrinkable thermoplastic polymer material having a main shrinkdirection parallel to the flute direction, means for continuouslydirecting the fluted first ply and a second ply of thermoplasticmaterial in face-to-face relationship to a laminating station, thelaminating station comprising laminating rollers between which heat andpressure is applied in laminating zones between the crests of the flutesof the fluted first ply and the second ply whereby bonding zones areformed extending in continuous or discontinuous rectilinear lines alongthe crests of the flutes at which the plies are bonded to one another,the apparatus further comprising a heat shrink station in which thefirst ply in the bonded product is heated to its heat shrink temperatureand allowed to shrink, the bonding zones being adapted to allow thesecond ply to become fluted upon shrinkage of the first ply, thewavelength of the fluting being less than 5 mm; an apparatus in whichthe second ply is fed to the laminating station as a substantiallyplanar web; an apparatus in which the laminating station comprises apair of grooved rollers, between which the heat and pressure is appliedfor lamination, the grooves of the laminating roller in contact with thefirst ply being parallel to and under operating conditions, having thesame pitch as the grooves of the fluting roller for the first ply, andthe grooves of the laminating roller in contact with the second plybeing arranged at an angle, preferably substantially perpendicular tothese grooves; an apparatus in which the laminating station comprises agrooved laminating roller and a substantially smooth counter rollerbetween which the heat and pressure is applied for lamination with thegrooved laminating roller in contact with the first ply; the grooves ofthe grooved laminating roller being parallel to and, under operatingconditions, having the same pitch as the grooves of the fluting rollerfor the first ply; an apparatus which comprises a stretching station forthe second ply at which the second ply is segmentally stretched in solidstate to produce first attenuated zones extending in a direction at anangle to the direction of the flutes of the first ply, preferablyperpendicularly thereto, wherein the substantially smooth laminatingroller is heated to a temperature which heats the opposite surface ofthe second ply in the first attenuated zones to the laminatingtemperature while the adjacent areas do not reach that temperature.

PCT/EP03/15001 DISCLOSURE

BRIEF DESCRIPTION OF THE DRAWINGS

The invention shall now be explained in further detail with referencesto the drawings.

FIGS. 1, 2, 3, 4 and 5 are cross-sections representing four differentstructures of the laminate of the invention, comprising the miniflutedply A, or plies A and D, and the straight ply B or plies B and C. Theflutes in each of these structures can extend longitudinally ortransversely, seen in relation to the machine direction of theflute-forming and laminating machinery.

FIG. 6 is an enlarged detail of FIG. 1 to illustrate how these pliesthemselves can be laminates of films, and how these films can bemultilayered as made by co-extrusion, this being done to facilitatebonding and lamination.

FIG. 7 is a principal sketch representing the steps from formation ofthe miniflutes in A to lamination of A with B in the manufacture of theproduct shown in FIG. 2, the different steps being represented by thecross-sections of the films A and B and by the cross-sections throughthe axis of the rollers of the surfaces of the rollers.

FIG. 8 is a sketch of the machine line corresponding to FIG. 7 withaddition of the means to laminate straight film C to A opposite to B.

FIGS. 9 a, 9 b and 9 c are sketches illustrating the cross-laminate ischaracterized in that A and B each has a main direction of orientation,either by being uniaxially oriented or unbalanced biaxially oriented, orby in itself being a cross-laminate of uniaxially oriented or unbalancedbiaxially oriented films, such cross-laminate exhibiting a resultantmain direction of orientation, whereby the resultant main direction oforientation in A is generally parallel with the longitudinal directionof the flutes, while the resultant main direction of orientation in Bforms an angle to the said direction in A.

FIGS. 10 a, b and c represent sections parallel to the flutes andthrough the middle of a non-bonded zone, showing applications of theinvention in which the channels or pockets formed between ply A and plyB are used as mini-containers or to canalize a flow of air or water,namely in FIG. 10 a as mini-containers for a protective agent, in FIG.10 b for filtration and in FIG. 10 c for weather protection.

FIG. 11 shows a modification of the lamination station of FIG. 8 inwhich there are added filling devices to fill particulate material intothe flutes before the lamination, and added sealing equipment to formtransverse seals after the lamination, thereby making closed pocketswhich serve as “mini-containers” for the particulate material.

FIG. 12 is a flow-sheet showing a process for producing the laminatewith transverse fluting and with “first” and “second” attenuated zones(as these expressions have been defined).

FIG. 13 shows a detail of a grooved lamination roller for formation oftransverse fluting, air jets being used to direct the ply into thegrooves and vacuum being used to retain it there.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention shall now be explained in further detail with reference tothe drawings.

FIG. 14 is a perspective view of the laminate of the invention, showingthe two plies A and B, each supplied with flutes, with the directions ofthe flutes in the two plies crossing each other, here as it normallywill be the case, perpendicular to each other. A part of ply A isremoved in order better to show the structure. The two plies are joinedby spot-welding within the areas (1) shown by interrupted lines.

FIGS. 15 and 16 are cross sections representing two different structuresof ply A. The section is made through a crest of B, which spot-wise isbonded to crests of A, and therefore the corrugated structure of B doesnot appear from these figures.

FIG. 17 is a principal sketch representing the steps from formation ofthe miniflutes in A to lamination of A with B in the manufacture of theproduct shown in FIG. 15, the different steps being represented by thecross sections of A and B and by the cross sections of the surfaces ofthe rollers (crosssections through the axis of the rollers).

FIG. 18 is a sketch of the machine line corresponding to FIG. 17. Theformation of flutes in B does here take place entirely by shrinkage of Aafter the lamination.

FIG. 19 is an enlarged detail of FIG. 14 to illustrate how these pliesthemselves can be laminates of films, and how these films can bemultilayered as made by coextrusion, this being done to facilitatebonding and lamination.

FIGS. 20, 21 and 22 represent sections parallel to the flutes in ply Athrough the middle of a non-bonded zone in this ply, and through thebonded crests in ply B (therefore corrugations on B cannot be seen)showing applications of the invention in which the channels or pocketsformed between ply A and ply B are used as mini-containers or tocanalize a flow of air or water, namely in FIG. 20 as mini-containersfor a protective agent, in FIG. 21 for filtration and in FIG. 22 forweather protection.

FIG. 23 shows a modification of the lamination station of FIG. 21 inwhich there are added filling devices to fill particulate material intothe flutes before the lamination, and added sealing equipment to formtransverse seals after the lamination, thereby making closed pocketswhich serve as minicontainers for the particulate material.

FIG. 24 is a flow-sheet showing a process for producing first and secondattenuated zones (as these expressions have been defined), in thetransversely oriented B, make transverse flutes, and laminate B with A.The latter has preformed flutes made as shown in FIGS. 17 and 18.

FIG. 25 shows a detail of a grooved lamination roller for formation oftransverse fluting, air jets being used to direct the ply into thegrooves and vacuum being used to retain it there.

FIG. 26 is a modification of FIG. 14 to illustrate the embodiment of theinvention in which there is a first set of holes at one surfaces and asecond set of holes at the other surface, whereby the two sets of holesare mutually displaced, so that a fluid passing into the holes at onesurface has to penetrate through a channel system before it can get outon the other surface. The channel system may e.g. be hydrophobic.

FIGS. 27 and 27 a are sketches showing segments of two roller unitsadapted to work together and produce the system of perforationsillustrated by FIG. 26. The rollers have spikes, (205) and (202) andoperate beyond the melting point of the polymer material. FIG. 27 is forperforation of flutes 2 a perpendicular to the machine direction andFIG. 27 a for perforation of flutes which follow the machine direction.

DETAILED DESCRIPTION OF THE INVENTION

With references to FIGS. 1 to 5 it should be mentioned for the sake ofclarity, that the wavelength referred to in the foregoing and in theclaims, is the straight linear distance from x to z. This distance ispreferably 3 mm or lower, and as it appears from the example, theinventor has been able to make it as small as 0.8 mm, which howeverneeds not be the ultimate lower limit obtainable and useful. It is notedthat U.S. Pat. No. 5,441,691 (Dobrin et al.) makes embossed film (notheat-bonded laminates having a generally circular shape of the bosses,with a spacing from center to center which can be still finer than these0.8 mm, however the bosses of this patent are drawn much thinner thanthe main body of the film.

In FIG. 1 the thickness of ply A is generally the same across the ply.In case of transverse fluting this can be achieved by the process shownin FIG. 12 (without preceding formation of attenuated zones) howeverthere is a limit, which is of practical importance, of how fine thewavelength can be, seen in relation to the thickness of ply A.

In case the flutes are made parallel with the machine direction, forformation of the flutes and the lamination is preferably carried outgenerally as shown in FIG. 8. This means there will always be atransverse stretching between intermeshing grooved rollers, and thedegree of fluting will correspond to the degree of stretching. When filmis stretched between very fine grooved rollers, there will be a strongtendency to localize the stretching entirely or predominately on andnear to the tips of the grooves. This can be avoided, but withdifficulty, by using film which in a preceding process has beentransversely stretched, and feeding the film unto the roller at atemperature which is higher than the temperature of the roller.

However, in the laminate structures shown in FIGS. 2 to 5 thedifferences of thickness resulting from grooved roller stretching hasbeen utilized in a way which generally is an advantage for theproperties of the product. By the exact registration between the groovedrollers for stretching, the grooved roller for lamination and a groovedtransfer roller therebetween, it is arranged that each bonding zonemainly falls within an attenuated zone. As it appears from FIG. 3 therecan be two sets of attenuated zones for each zone of bonding, namely aseries (6) of wider ones (lithe first attenuated zones”) within whichthe bonding zones fall, and a set of shorter ones (101), the latterreferred to as the “second attenuated zones”.

By attenuating ply A at the basis where it is bonded to ply B, thethickness of A is minimized at the location where its contribution tostiffness in the stiff direction in any case is insignificant. Byintroducing the narrow “second attenuated zones” which act as “hinges”,the cross-section becomes almost triangular as shown in FIG. 3. Thismeans that the stiffness is further improved attenuated zones alsointroduce a tendency in the material to stretch rather than ruptureunder impact actions.

To clarify the concepts, each first attenuated zone (6) is perdefinition delimited by the locations (102) where the thickness of ply A(or ply D) as indicated by arrows is the average between the smallestthickness in this zone and the highest thickness in the adjacentnonbonded zone.

Structures with “first attenuated zones” as shown in FIGS. 2 to 5 andstructures with both “first and second attenuated zones”, as shown inFIG. 3 can also be produced with machinery which make transversefluting. This shall be described later.

In FIG. 6 both plies A and B are in themselves laminates, for instancecross-laminates are characterized in that A and B each has a maindirection of orientation, either by being uniaxially oriented orunbalanced biaxially oriented, or by in itself being a cross-laminate ofuniaxially oriented or unbalanced biaxially oriented films, suchcross-laminate exhibiting a resultant main direction of orientation,whereby the resultant main direction of orientation in A is generallyparallel with the longitudinal direction of the flutes, while theresultant main direction of orientation in B forms an angle to the saiddirection in A, and each film from which the plies are produced isco-extruded. Therefore A and B are each formed by a lamination process(the“pre-lamination”) prior to the lamination of A to B. Layer (1) isthe main layer in each of the two coex films which make A, and layer (2)is the main layer in the two coex films which make B. Layers (1) and (2)can e. g. consist of high density polyethylene (preferably HMWHDPE) oriso- or syndio-tactic polypropylene (PP) of blends of one of thesepolymers with a more flexible polymer, for instance, for HMWHDPE, LLDPE.If stiffness is the most preferred property of the minifluted laminate,plain HMWHDPE or plain PP may be chosen, but if tear and punctureproperties play a more important role and/or superior heatsealproperties are essential, the mentioned blends may be more suited.

Layers (3) are coextruded surface layers with the function to improvethe heat-seal properties of the finished, minifluted laminate and/ormodify its frictional properties. Layers (4) are co-extruded surfacelayers (“lamination layers”) with the two functions: a) to facilitatethe pre-lamination and b) to control the bonding strength (incross-laminates the bonding should not be too strong, otherwise the tearpropagation strength suffers).

Similarly, layers (5) are co-extruded surface layers to facilitate thelamination of the entire A to the entire B and control the strength ofthe bonding between A and B.

With reference to FIG. 7 and FIG. 8 the structure shown in FIG. 2 can beformed by passing film (A) first over the grooved pre-heating roller (6a) which heats it only along the lines which shall become attenuated,then over the grooved stretching rollers (7) and (8), further overgrooved transfer and flute-stabilizing roller (9), and finally overgrooved lamination roller (10) and its rubber-coated counter-rollers(11), while film (B) is passed over the smooth rollers (12) and (11).The grooves of all of the rollers are circular so that the flutes areformed in the machine direction. If B is transversely oriented andtherefore has a tendency to transverse shrinkage, rollers (12) and (11)are preferably supplied with devices, e.g. belts, to hold the edges (notshown). All of these rollers are temperature controlled rollers, rollers(9), (10), (11) and (12) being controlled at the lamination temperature,rollers (6 a) and (8) at a somewhat lower temperature and roller (7) ata temperature about 20 or 30° C. (There can be further rollers forpreheating of B). By choice of suitable, coextruded surface layers—see(5) in FIG. 6 the lamination temperature is kept far below the meltingrange of the main layers in (A) and (B). The temperature of the zones(6) in (A) during the transverse stretching between rollers (7) and (8)is preferably still lower, e.g. in the range of about 50-70° C. and therest of (A) much lower, e.g. around room temperature, as it also appearsfrom the mentioned roller temperatures. If the main layers in (A) and(B) consist of plain HDPE or blend of HDPE and LLDPE, the laminationtemperature is preferably chosen between about 80 and about 110° C., andthe coextruded lamination layers, which can consist of a suitable plainor blended copolymer of ethylene, are chosen to produce lamination atthis temperature.

The crests on roller (8) has very small radius of curvature, e.g. about0.05 mm or an extremely narrow “land”. The crests on roller 6 a whichhave the function to preheat, may, depending on the film, be similar orsomewhat rounder or with a slightly wider land. The crests on rollers(7) and (9) have a higher radius of curvature or a wider land, to avoidtransverse stretching on these crests. Suitable values for the sizes ofthe grooves are mentioned below in the example.

The different temperatures on the different grooved rollers causedifferent thermal expansions, compared to a state where all have roomtemperature, and this must be taken into consideration when the groovedrollers are constructed, since they must fit exactly to each otherduring operation. (10° C. heating of a 10 cm long steel roller segmentcauses about 0.011 mm expansion of this segment). Reference is againmade to values in the example.

Rollers (7), (8) and (10) are driven, while rollers (6 a), (9), (11) and(12) may be idling.

As it will be understood, the attenuation of A in the zones (6) takesplace almost entirely by the transverse orientation at a temperatureessentially below the melting range of the main body of A. Thisattenuation therefore does not cause any significant weakening of A'stransverse strength, contrarily it will normally cause an increase ofthis strength. After the transverse stretching on the crests of roller(8) the width of the “first attenuated zones” (6) should preferably notexceed (as a rule of the thumb) half the wavelength, but the degree ofstretching should normally be as high as practically obtainable, whilethe degree of transverse stretching between the “first attenuated zones”normally should be as low as practically obtainable, with the intendedresult that ply A in the unbonded zones becomes as thick as the chosensquare meter weight of A allows and the flutes become as high aspossible.

A practical way of achieving that the first attenuated zones and thezones of bonding match with almost equal width is the following: therelatively flat crests on the laminating roller (10) are made slightlywider than the chosen width of the first attenuated zones, and thetemperature and velocities are adjusted to each other in such a way thatthe first attenuated zones (6) become heated to a temperature at whichthe material will laminate with B, while the thicker A-ply between zones(6) does not reach a temperature at which lamination can take place.

The use of longitudinally oriented A-ply characterized in that A, withineach non-bonded zone and outside the first attenuated zone if such zoneis present, is molecularly oriented mainly in a direction parallel tothe direction of the flutes or in a direction close to the latter asdetermined by shrinkage tests will impart a tendency in A to “neck down”and form thin longitudinal lines when A is stretched transversely.Therefore, longitudinally oriented A-ply will enhance the possibilitiesof getting a sharp distinction between strongly attenuated zones (6) andnon-attenuated ply A between these zones.

Theoretically there will always occur some attenuation also of the B-plyin the zones of bonding, since the bonding is established underpressure, but this attenuation has no positive effect and shouldpreferably not exceed 20%. Due to the presence of lamination layers (see(5) in FIG. 6) such attenuation of the B-ply can be made negligible.

In FIG. 8 the minifluted laminate leaving lamination rollers 10 and 11is marked (B/A), In this figure it proceeds for lamination inconventional manner with the non-waved, mono-/or multilayered film Ccoming from the smooth steel roller (13). The lamination takes placebetween the smooth steel rollers (14) and (15) of which at least roller(14) is heated to a convenient lamination temperature and is driven. Thewaved film A is heated to lamination temperature, at least on its freecrests, by means of hot air from the blower (16). Rollers (14) and (15)are kept at a distance from each other which is small enough to effectthe lamination but big enough to avoid excessive flattening, e.g.between 0.2 and 0.6 rom. h˜en A, B and C are very thin films, e.g. eachin the range of 0.03-0.10 mm thick (for A this refers to the non-wavedform) such conventional lamination would have been very difficult due tothe floppiness of waved A, but since the flutes now have beenconsolidated by the bonding to B, the lamination of A to C presents noparticular difficulty.

The laminate leaving-the lamination rollers (14) and (15) is markedB/A/C. It is cooled, e.g. by air (not shown) and may normally be reeledup or flip-flopped, since it normally is sufficiently flexible materialalthough fluted, or it may directly be cut into lengths.

To make the laminate shown in FIG. 5, one option is to make the A/Blaminate shown in FIG. 2, and laminate this over the rollers (11)—and(10) with the fluted ply D leaving roller (9). This requires exactregistration between the rollers which make the A/B laminate and roller(1)). Alternatively B can consist of e.g. two films B1 and B2. Then intwo mutually independent processes there are made an A/B1 laminate and aD/B2 laminate, and the two are bonded together with B1 against B2 in anextrusion lamination process.

With certain modification the line shown in FIGS. 7 and 8 can also beused to make the laminate of FIG. 3, which has “second attenuatedzones”. For this purpose roller (6 a) should have the same surfaceprofile and the same low temperature as roller (7), and it should bepreceded by and in slight engagement with a roller with the same surfaceprofile as roller (8), which roller should have the same highertemperature as roller (8).

In the minifluted “multi-crosslaminate” shown in FIGS. 9 a, 9 b and 9 c,the two coextruded films (1 a) and (1 b) from which A is made by“pre-lamination”, are oriented in criss-crossing directions, which forman angle lower than 45° with the longitudinal direction (the flutedirection) as symbolized by the arrows (1 aa) and (1 bb). This gives aresultant main orientation direction for A parallel with the flutedirection, symbolized by the arrow marked A′. Similarly the twocoextruded films (2 a) and (2 b) from which B is made by“pre-lamination”, are oriented in criss-crossing directions, which forman angle higher than with the flute direction, as symbolized by thearrows (2 aa) and (2 bb). This gives a resultant main orientationdirection of B perpendicular to the flute direction, symbolized by thearrow B′.

In FIG. 10 a, which as mentioned shows a longitudinal section through aflute in ply A, the latter has been flattened and sealed to ply B atintervals (103) to form pockets or “mini-containers” and thesemini-containers have been filled with a particulate substance (104)which has a purpose for the use of the laminate, e.g. for protection ofmaterial packed or wrapped up in the latter. As one among many optionsit may be an oxygen scavenger. To enhance the action of the substancethe flutes may be supplied with fine perforations on the side towardsthe packed product. The substance may also e.g. be a fire retardantmaterial such as CaCl₂ with crystal water, or just fine sand to increasethe bulk density of the laminate.

FIG. 11 which shall be described below, shows how the particulatesubstance can be fed into the flutes of ply A prior to its laminationwith ply B, and how the flutes can be closed to pockets by transversesealing after the lamination, without any essential contamination ofthese transverse seals.

A laminate between a fluted thermoplastic film and a non-flutedthermoplastic film with a filling material between is known fromJapanese Patent publication No. 07-276547 (Hino Masahito). However, inthis case the filling material is a continuous porous sheet (forabsorption) which extends from flute to flute without interruptions, sothat there is no direct bonding between the flute and the non-flutedfilms. One of the thermoplastic films is first directly extruded untothis porous (e.g. fiberformed) sheet, then the two together are given afluted shape between gear rollers while the thermoplastic film still ismolten, and finally a second thermoplastic film is extruded directlyunto this fluted assembly to join with the porous sheet. Hereby thebonding necessarily must be very weak, and the mechanicalcharacteristics must be completely different from those of the presentproduct. The wavelength of the fluting is not indicated.

In the technical filter material for liquid or gas flows shown in FIG.10 b there is inserted a strand or yarn into each flute—in connectionwith the description of FIG. 11 it shall be explained how that can bedone—and both sides of each channel formed by fluted ply A and nonflutedply B is supplied with a row of perforations, (106) in ply A and (107)in ply B. These rows are mutually displaced as shown so that the liquidor gas passing from one surface of the laminate to the other, is forcedto follow a channel over a distance corresponding to the displacement.The fitting between the yarn and the channel may be improved byshrinkage of A and/or B after the lamination process.

The pocket structure shown in FIG. 10 a can also be used for filtrationpurposes if ply A and ply B are supplied with mutually displaced holes.Then the particulate substance (104) can e.g. consist of activecharcoal, or an ion-exchange resin, or for simple filtration purposesfine sand. Also in this case a tightening of the passage by means ofshrinkage can be advantageous or may even be essential.

Practical examples of the use of such filter materials are for airfiltration systems including absorption of poisonous substances, andion-exchange processes. In both cases the laminate can have the form ofa long web which is slowly advanced transversely to the flow whichpasses through it.

Another practical use is as a substitute of geotextiles e.g. for roadconstructions. Such textiles must allow water to penetrate but hold backeven fine particles. The present laminate, e.g. filled with fine sand inthe pockets, is suitable for this use.

For such filtration purposes, high puncture strength will often beneeded, and the laminate then preferably comprises oriented,cross-laminated films.

For the filtration purposes the condition that the wavelength should notexceed 3 mm, is often less important since appearance and handle may notbe a primary concern as it is in the case of laminates for ordinarytarpaulin uses.

The weather protective laminate shown in FIG. 10 c, e.g. for raincoats,also has a pocket structure, whereby ply A is heat-sealed to ply B bytransverse seals at locations (103), but there is no particulatesubstance in the pockets. Like the laminate for filtration, each line ofpockets is supplied with perforations in a displaced system, here shownas groups of perforations (109) in A and similar groups (110) in B, andthese groups are mutually displaced. In this sketch it is consideredthat ply A is on the side where it rains, and a person, animal or item,which the laminate shall protect, is on the ply B side. (It could be theother way round). It is also considered that the direction shown byarrow (108) is upward. Since the perforations (109) are at the bottom ofthe pockets, and because of the gravity force, only the bottom of thepockets may be filled with rainwater, while in principle no water willreach the perforations (110). On the other hand there is free passage ofair and transpiration between the hole groups (109) and (110). Also inthis product the wavelength may to some extent exceed 3 mm.

The modification of the FIG. 8 machine-line, which is shown in FIG. 11,is adapted to fill a particulate substance (104) into the channelsformed between A and B. The filling is here shown very schematically.The powder (104) is taken from a hopper (111) and is administered bymeans of an adjustable vibrator (not shown). It falls into the flutedply A at the upper side of the grooved lamination roller (10). Atregular time intervals hopper (111) is filled up with the powder (104).The means for this are not shown. Other conventional systems foradministering the powder (104) onto ply A on roller (10) may of coursebe chosen.

Roller (10) vibrates (means not shown) so that the powder is moved fromthe higher zones, i.e. those which become bonded zones when A meets B inthe nip between (10) and (11), into the lower zones, which become the“channels”.

Having left the laminating rollers (10) and (11). The A+B-laminate withpowder (104) in the channels moves towards the cog-roller (113)—itssurface is shown in a detailed part-drawing and its rubber-coatedcounter-roller (114) which together flatten and close the channels bymaking transverse seals. Roller (113) is vibrated in order to removepowder away from the channel-parts which become flattened and sealed.

Both rollers (113) and (114) are heated to a temperature needed for thesealing, and since the laminate while entering these rollers still is atabout a temperature suitable for heat-sealing due to the previoustemperatures, this second heat-seal process needs not cause adeceleration of the entire process.

Ply A and/or ply B may be perforated by means of pin-rollers afterrollers (10)/(11) and in front or after the pair of rollers (113)/(114).In case mutually displaced rows of perforations are needed (see FIGS. 10b and c) and pin-rollers for ply A and ply B must be suitablycoordinated, and in case the perforations should have a fixed relationto the transverse seals (see FIG. 10 c, the pin-rollers must becoordinated with roller (113).

In order to make the product shown in FIG. 10 a, rollers (113) and (114)are omitted or taken out of function, and instead of administeringpowder into ply A, there is at the same place laid a yarn into eachflute. Each yarn is taken from a separate reel.

At some stage after rollers (10)/(11), ply A and/or play B may besubjected to transverse shrinkage. If this is done with ply A only, itmay be sufficient to heat the ply A-side of the laminate to an adequatetemperature by means of hot air or on one or more hot rollers. If ply Bshould be involved in the shrinkage it may be necessary to hold thelaminate at the edges while it shrinks. This may be done by means of anordinary tenterframe, but the latter should be set up to work“inversely” so that the width gradually is reduced instead of increased.

The methods applied for making pockets from the flutes, fill powder intothese flutes, and making suitable perforations, have been explained inconnection with the longitudinally fluted laminate. Analogous methodscan be applied in connection with a transversely fluted laminate (thegeneral method of making such laminate appears from FIG. 12), and inthat case the closing of the channels to form pockets may take place byuse of a circularly or helically grooved roller. However, it is notconsidered practically possible to lay down yarn in transverse flutes atindustrially acceptable velocities.

The process for making the transversely fluted laminate, which appearsfrom the flow-sheet FIG. 12 is generally analogous to the process whichis described in connection with FIGS. 7 and 8, and the profiles of thegrooved rollers can also be generally similar, except that for theprocess of FIG. 12 the grooves extend axially, while for the process ofFIGS. 7 and 8 they are circular.

Step 1: Ply A is longitudinally stretched in very narrow zones localizedon the tips of a hot roller which has a profile similar to that ofroller (8). The grooved counter-roller, which is cold, has a profilelike that of roller (7).

Step 2: The warm, stretched “second attenuated zones” are cooled on acold grooved roller which also has a profile like that of roller (7),and then to form “first attenuated zones” between the “second”, ply A islongitudinally stretched between this cold roller and a warm groovedroller which also has a profile similar to that of roller (8). Thestretching is localized to the tips of this roller. Similar to theregistration in printing technology, step 2 is brought in registrationwith step 1 under use of a device which optically detects the stretchedzones.

Step 3: The flutes are first formed in the grooves of a hot roller witha profile similar to that of roller (10), e.g. under use of compressedair, and are held in the grooves e.g. under use of a vacuum, all asexplained in connection with FIG. 13, and ply A is then laminated withply B between the crests of this grooved roller and a rubber-coatedcounter-roller, which also is heated. Ply B has been preheated.

There can be different after treatments as explained in the foregoing.

In FIG. 13, ply A which has been supplied first with the very narrowtransverse “second attenuated zones” (101), and then with the somewhatwider, also transverse “first attenuated zones” (6), is directed intothe grooves (115) of the heated lamination roller by means of compressedair from a row of nozzles of which one (116) is shown. By use ofregistration means, working on basis of optical detection of zones (6)or (101) it is arranged that the first attenuated zones (6) will coverthe crests (118) of the grooved roller. The two sets of attenuated zonesact as hinges so that even a quite heavy ply A may be bent and form theflutes. The latter are held in shape in the grooves under use of vacuumapplied through channels (117) from the interior of the roller. Thus plyA is moved in flute shape to the nip (not shown) between the groovedroller and the rubber-coated counter-roller, where lamination takesplace. The vacuum in the grooves is adjusted so that ply A is heldfirmly when this is needed, but can be released where that is needed.There can also be a valve arrangement inside the grooved roller toeliminate the vacuum during the release.

EXAMPLE

A 2-ply laminate of fluted ply A and non-fluted ply B with Alongitudinally and B transversely oriented is manufactured on apilot-unit constructed as shown in FIGS. 7 and 8, but terminating afterthe lamination of A and B have taken place. Both plies consist of onecoextruded, cold-stretched 0.037 mm thick film consisting of HOPE with athin layer-on one side, consisting of an ethylene copolymer having amelting range between 95-105° C. This is used as lamination layer in theprocess. The cold-stretching was carried out near room temperature at adraw ratio about 3:1 and was followed by heat stabilization, all byconventional means, and while the film had flat tubular form. The tubewas longitudinally cut to form ply A.

Processes for continuous manufacture of transversely oriented film arewell-known and mentioned in the foregoing but it would have causedpractical complications for the inventor to have such film manufacturedaccording to his specifications, and therefore short lengths of the plyA-film were glued together edge to edge with a pressure-sensitiveadhesive to form a transversely oriented web.

All of the grooved rollers have the pitch 1.1000 mm at the temperatureat which they actually are used, but due to the large temperaturedifferences during the stretching/laminating process, the thermalexpansion had to be taken into consideration when these rollers weremachined at 20° C., see the table below. The biggest temperaturedifference between the rollers, as it appears from this table, is 85°,and this corresponds to an expansion of about 0.10 mm per 10 cm rollerlength, while the accumulated error in the fitting between adjacentrollers from end to end of the rollers must be maintained lower than0.15 mm to obtain the needed registration.

The table below also indicates the radius of curvature (R) or the lengthof a “land” on the crest of each grooved roller, as seen in the axialsection in FIG. 7.

Roller No. 6a 7 8 9 10 Crest land R = land R = Land mm 0.4 0.2 0.15 0.150.7 Temperature 70 20 70 105 105 ° C. Pitch mm 1.0993 1.1000 1.09931.0988 1.0988

It is of course not practically possible to achieve such a high accuracyin the pitch seen individually from groove to groove, but it isessential that errors in the pitch do not accumulate by more than 0.05mm. This is best achieved when the surface parts are made from segmentsand accumulated errors are eliminated by fine grinding of the segmentends and/or thin shims (foils) are inserted between the segments. In theactual pilot machine the length of the grooved part of each rollersurface was about 450 mm and was assembled from 3 segments. It is judgedthat in an industrial machine the rollers can be made in up to about 5 mlength, but in that case the accuracy from end to end has to be checkedwith laser measurements and adjustments made as explained.

The transverse stretching, which is the basis for the flute-formationand which forms the “first attenuated zones”—later the zones whichbecome bases, not crests of the flutes in the laminate—takes place bythe intermeshing between rollers (7) and (8) and becomes localized to azone on and nearby the crests of roller (8). This is because roller (8)is hot and has a relatively sharp crest, while roller (7) is cold andhas a much rounder crest (higher radius of curvature R). It is relevantalso in this connection that ply A is uniaxially oriented in the machinedirection and therefore has a high tendency to “neck-down” and formsharply delimited attenuated zones when it is transversely stretched.

The function of roller (6 a) is to preheat the zones which are to bestretched on the tips of roller (a). In this example the “land” on thecrests of roller (6 a) are wider than the “land” on the crests of roller(8). This has been chosen in order to counteract the very pronouncedtendency in the film to “neck-down”, in other words, to make the limitsof the “first attenuated zones” smoother. In other cases e.g. when ply Ahas a pronounced transverse orientation and therefore no tendency to“necking down” by transverse stretching, the “land” on the crests ofroller (6 a) which preheats the film, should be no wider than the “land”on the crests of roller (8).

Between rollers (6 a) and (7) there is a slight but almost zeroengagement to avoid wrinkles without stretching the films.

Having left the transverse stretching roller (8), ply A is taken over bytransfer roller (9). This is heated in order to help the shaping offlutes in the zones which have not been stretched. At this stage the“first attenuated zones” are still deeply curved, but when (A) is takenover by the flat 0.4 mm wide crests (lands) on the grooved laminatingroller (10) the “first attenuated zones” are flattened almost over theirentire width except at their boundaries where the thickness graduallyincreases, and by means of the rubber-coated counter-roller, which onits surface has temperature 80° C., this flat portion is laminated tothe transversely oriented ply B.

Prior to the experimental run the axial position of the grooved rollersare very carefully adjusted to each other, and so is the intermeshingbetween adjacent grooved rollers. The intermeshing between rollers (7)and (8) is set to make the depth of the fluting 0.40 mm, as measured inmicroscope on a cross-section of the finished laminate.

When leaving the stretching/laminating apparatus, the miniflutedlaminated is aircooled and is reeled up on a core of diameter 250 mm. Inthe test report below this laminate is called “Sample I”.

It is noted that although the pitch of each grooved roller in the lineis 1.1000 mm referring to the temperature at which the roller has beenoperated, the wavelength of the fluting in the final miniflutedlaminate, due to transverse shrinkage, is only 1.0 mm.

As a principal experiment there is out specimens of this film, 30 cmlong in the machine direction and 20 cm wide in the transversedirection, and these specimens are subjected to further transverseshrinkage by a primitive arrangement which imitates an “inverse”operation of a tenter frame. The two 30 cm long edges are fixed to twosticks, which are held by hand, and an even shrinkage is arranged bymoving the specimen over a roller surface, which is heated to 115° C.,with the B film contacting the roller. Hereby the wavelength is reducedfrom 1.0 mm to 0.8 mm.

Sample II made for comparison: By a relatively primitive arrangementthere is made specimens of corrugated board material from the same filmas used to make “Sample I” (coextruded cold stretched HDPE-film ofthickness 0.037 rnm), with all dimensions of sample A, namely asfollows:

Wavelength Bonded Zones Flute-depth Sample mm mm mm I 1.0 0.4 0.4 II 5.52.2 2.2

It is noted that II's wavelength, 6.0 mm, is slightly less than theminimum mentioned in patent literature namely in US-A-4.132.S81.

In both samples I and II, the direction of orientation in ply A isparallel with the flutes, and the direction of orientation in B isperpendicular to the flutes.

Sample B is manufactured with a small laboratory machine constructed asexplained in connection with FIG. 13, but in this case there has nowbeen any need to make “first attenuated zones” and “second attenuatedzones”. The flutes become perpendicular to the machine direction. Likethe grooved laminating roller (10) used in the manufacture of sample I,this grooved laminating roller is heated to 105° C.

Sample III, made for comparison: The same film (coextruded orientedHDPE, 0.037 mm thick) is crosslaminated with itself without any flutingbeing made.

Comparisons between samples I, II and III:

Appearance and Handle:

(II) looks and feels like a board material, but is instable when bent orcompressed between the fingers.

(I) has a rather textilis look, can stand a substantial amount ofbending and compression between the fingers without changing itscharacter, and it has a feel of “bulk”.

Bending Tests:

(I) and (II) are bent over cylindrical bodies of different diameters,and it is examined how small that diameter can be before the flutesbegin to collapse in a non-elastic manner, i.e. so that there remainmarks in the flutes after the specimen has been straightened out again.

(II) can withstand bending down to a diameter of 250 mm, while (I) canwithstand bending down to a diameter of 50 mm.

Stiffness Measurements:

10 cm long specimens are cut out from samples (I), (II) and (III).

The specimens from sample (I) each comprises 20 flutes and at the edgesa bonded zone. The width of these specimens is 21 mm.

The specimens from sample (II) each comprise 4 flutes and at the edges abonded zone. The width of these specimens is 23 mm.

The width of each sample (III) specimen is 21 mm.

For controlled bending of the specimens there is made a very lightweightsupport arrangement comprising two supports with 50 mm spacing between.This support arrangement is placed on the table of a letter balance. Thebending is effected by means of a cylinder which has a diameter 50 mmand starts pressing at the middle of the supported sample. This cylinderis assembled on a stand and can be moved up and down. Correspondingvalues of the depression in mm and the resisting force in grams aremeasured and plotted. Up to a certain limit there is a lineardependence, and from the declination of the line and stiffness iscalculated as grams force per mm depression. In order to obtain reliablereading for sample (III), 10 specimens are laid one on top of the other.The value of stiffness is determined for this bunch and divided by 10.

Results

Surprisingly samples (I) and (II) show the same stiffness, namely 1.6gram per mm, while sample (III) shows 0.13 gram per mm, in other wordsthe present invention has magnified the stiffness in one direction by afactor of about 12, as measured by this method.

It should have been expected that sample (III) would have shown higherstiffness than sample (I). When this is not the case,’ the explanationprobably is that the flutes may have been pressed relatively flat rightfrom the beginning of the depression, although in elastic manner.

In the characterization of the product and method of the invention, ithas been emphasized that the wavelength of the fluted ply A or the pitchon the grooved laminating roller should be no more that 3 mm in order togive the corrugated laminate the character of a flexible film ratherthan a board material. However, in connection with the description ofthe filter material, in which liquid or gas passes from holes in one plyto displaced holes in the other ply; and on the way passes a filler, itwas nevertheless stated that for such purposes the wavelength may exceedthe 3 mm. Similar is true for the described weather protectivecorrugated laminate, in which there also are displaced holes, butusually no filler, and the gravity force is used to “filter” therainwater from the passing air.

Furthermore, the making of “first attenuated zones” and optionally also“second attenuated zones” has been explained as useful measures forobtaining the “miniflutes”, be it in connection with longitudinally ortransversely fluted laminates. Since these zones act as “hinges” seee.g. FIG. 13—they enable for a given thickness of ply A a finerwavelength and/or deeper fluting then it otherwise could be achieved. Inthe foregoing there has also been stated other useful effects of the“fist attenuated zones” and the “second attenuated zones”, and it isclear that similar advantages can be achieved when the wavelength of theproduct or the pitch of the grooved lamination roller exceeds 3 mm.

Therefore the product and the making of the “first attenuated zones” andoptionally and “second attenuated zones” placed as it has been describedin the foregoing is considered an invention independently of thewavelength.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIGS. 15 and 16 it should be mentioned for the sake ofclarity, that the wavelength referred to in the foregoing and in theclaims, is the straight linear distance from x to z. This distance isnormally about 5 mm or lower, and as it appears from example 3, theinventor has been able to make it as small as 0.8 mm, which howeverneeds not be the ultimate lower limit obtainable and useful. It is notedthat US-A-S441691 (Dobrin et al) makes embossed film (not heat-bondedlaminates) having a generally circular shape of the bosses, with aspacing from center to center which can be still finer than these 0.8mm, however contrary to the present invention the bosses of this patentare drawn much thinner than the main body of the film.

In case the flutes are made parallel with the machine direction, theformation of the flutes and the lamination is preferably carried outgenerally as shown in FIGS. 17 and 18. This means there will always be atransverse stretching between intermeshing grooved rollers. When film isstretched between very fine grooved rollers, there will be a strongtendency to localize the stretching entirely or predominantly on andnear to the tips of the grooves. This can be avoided, but withdifficulty, by using film which in a preceding process to some extenthas been transversely stretched, and feeding the film into the roller ata temperature which is higher than the temperature of the roller.

However, in the laminate structures shown in FIGS. 14, 15 and 16. thedifferences of thickness resulting from grooved roller stretching hasbeen utilized in a way which generally is an advantage for theproperties of the product. By the exact registration between the groovedrollers for stretching, the grooved roller for lamination and a groovedtransfer roller therebetween, each bonding zone is arranged so as tofall mainly within an attenuated zone. As it appears from FIG. 16 therecan be two sets of attenuated zones for each zone of bonding, namely aseries (6) of relatively wider ones (the first attenuated zones) withinwhich the bonding zone fall, and a set of shorter ones (101), the latterreferred to as the second attenuated zones.

By attenuating ply A at the basis where it is bonded to ply B, thethickness of A is minimized at the location where its contribution tostiffness in any case is insignificant. By introducing the narrow secondattenuated zones which act as hinges, the cross-section becomes almosttriangular as shown in FIG. 16. This means that the stiffness is furtherimproved. In many cases, these attenuated zones also introduce atendency in the material to stretch rather than rupture under impactactions. To clarify the concepts, each first attenuated zone (6) is perdefinition delimited by the locations (102) where the thickness of ply Aas indicated by arrows is the average between the smallest thickness inthis zone and the highest thickness in the adjacent non-bonded zone.

Structures with first attenuated zones as shown in FIGS. 14, 15 and 16and structures with both first and second attenuated zones, as shown inFIG. 16 can also be produced with machinery which make transversefluting. This is described later.

In FIG. 19 both plies A and B are in themselves laminates, for instancecrosslaminates, and each film from which the plies are produced iscoextruded. Therefore A and B are each formed by a lamination process(the “pre-lamination”) prior to the lamination of A to B. Layer (1 a) isthe main layer in each of the two coextruded films which make A, andlayer (2) is the main layer in the two coextruded films which make B.Layers (1 a) and (2) can e.g. consist of high density polyethylene(preferably HMWHDPE) or iso- or syndio-tactic polypropylene (PP) ofblends of one of these polymers with a more flexible polymer, forinstance, for HMWHDPE, LLDPE. If stiffness is the most preferredproperty of the minifluted laminate, plain HMWHDPE or plain PP may bechosen, but if tear and puncture properties play a more important roleand/or superior heatseal properties are essential, the mentioned blendsmay be more suited.

Layers (3) are coextruded surface layers with the function to improvethe heatseal properties of the finished laminate and/or modify itsfrictional properties. Layers (4) are coextruded surface layers(lamination layers) with the two functions: a) to facilitate thepre-lamination and b) to control the bonding strength (in crosslaminatesthe bonding should not be too strong, otherwise the tear propagationstrength suffers).

Similarly, layers (5) are coextruded surface layers to facilitate thelamination of the entire A to the entire B and control the strength ofthe bonding between A and B.

With reference to FIG. 17 and FIG. 18 the structure shown in FIG. 15 canbe formed by passing film (A) first over the grooved pre-heating roller(6 a) which heats it mainly along the lines which shall becomeattenuated, then over the grooved stretching rollers (7) and (8),further over grooved transfer and flute-stabilizing roller (9), andfinally over grooved lamination roller (10) and its rubber coatedcounter-roller (11) which is supplied with axial grooves, while film Bunder low tension is passed over the smooth rollers (12) and (11). Thelaminate is taken off from lamination roller (10) over roller (13), thesurface shape of which has a very slight sinus shape seen in axialsection. The purpose of this shape shall be explained in the following.The grooves of all of the above mentioned grooved rollers, except therubber roller, are circular so that the flutes of A are formed in themachine direction. These rollers are all temperature controlled rollers,rollers (9), (10), (11) and (12) being controlled at the laminationtemperature, rollers (6 a), (8) and (13) at a somewhat lower temperatureand roller (7) at a temperature about 20 or 30° C. (There can be furtherrollers for preheating of B). By choice of suitable, coextruded surfacelayers—see (5) in FIG. 19—the lamination temperature is kept far belowthe melting range of the main layers in (A) and (B). The rubber coatedroller (11) is preferably heated by a combination of heating from withinand heating from outside (by hot air or infrared irradiation). Thetemperature of the zones (6) in (A)—reference to FIG. 15—during thetransverse stretching between rollers (7) and (8) is preferably stilllower, e.g. in the range of about 50-70° C., and the rest of (A) muchlower, e.g. around room temperature, as it also appears from thementioned roller temperatures. If the main layers in (A) and (B) consistof plain HDPE or blends of HDPE and LLDPE, the lamination temperature ispreferably chosen between 80 and 110° C., and the coextruded laminationlayers, which consist of a suitable plain or blended copolymer ofethylene, are chosen to produce lamination at this temperature.

Ply A is longitudinally oriented prior to the processes shown in FIGS.17 and 18, under conditions which gives it a tendency to shrink, e.g.10-25% shrinkage when heated to the lamination temperature. Theformation of flutes in B is based on such shrinkage of A.

Ply B is transversely oriented prior to these processes, therefore alsohas a tendency to shrink. This shrinkage will ruin the process if notproperly dealt with. In the drawing it is done by means of groovedrollers 14 a and b which give B a pleating sufficient to compensate forthe shrinkage and exactly adjusted for this. This means that on the hotroller 12, B shrinks evenly all over its width in a degree which just isenough to eliminate the pleats. These grooved rollers have a high pitch(see example 1), are set up to pleat without transverse stretching, workat room temperature, and are idle rollers which almost do not increasethe tension in the film.

The crests on roller (8) have very small radius of curvature, e.g. about0.07 mm or a similarly narrow land. The crests on roller (6 a) whichhave the function to preheat, may, depending on the film, be similar orof a somewhat’ greater radius or with a slightly wider land. The crestson rollers (7) and (9) have a bigger radius of curvature to avoidtransverse stretching on these crests. Suitable values for the sizes ofthe grooves are mentioned below in example 1.

The different temperatures on the different grooved rollers causedifferent thermal expansions, compared to a state where all are at roomtemperature, and this must be taken into consideration when the groovedrollers are constructed, since they must fit exactly to each otherduring operation. (10° C. heating of a 10 cm long steel roller segmentcauses about 0.012 mm expansion of this segment). Reference is againmade to values in the example.

Rollers (6 a), (7), (8), (9), (10), (12) and (11) are driven, the lastthrough (10), while rollers (13), (14 a) and (14 b) may be idling.

As it will be understood with reference to FIG. 15, the attenuation of Ain the zones (6) takes place almost entirely by the transverseorientation at a temperature essentially below the melting range of themain body of A. This attenuation therefore does not cause anysignificant weakening of A's transverse strength, contrarily it willoften cause an increase of this strength. After the transversestretching on the crests of roller (8) the width of the first attenuatedzones (6) should preferably not exceed (as a rule of thumb) half thewavelength, but the degree of stretching should normally be as high aspractically obtainable, while the degree of transverse stretchingbetween the first attenuated zones normally should be as low aspractically obtainable, with the intended result that ply A in theunbonded zones becomes as thick as the chosen square meter weight of Aallows and the flutes become as high as possible. However, when there isreliance on a shrinkability in A as in example 1, the heating of ply Aon roller 9 will cause a tension which tends to reduce the thickness inthe unbonded zones and correspondingly increase the depth of the flutes.

The use of longitudinally oriented A-ply will impart a tendency in A toneck down and form thin longitudinal lines when A is transverselystretched on roller 8.

Therefore, longitudinally oriented A-ply will enhance the possibilitiesof getting a sharp distinction between strongly attenuated zones (6) andnon-attenuated ply A between these zones.

The line of rollers (6 a) to (10), which ply A follows, should normallyrotate at equal circumferential velocity. Thus the heating and A'slongitudinal orientation will have given A a rather high longitudinaltension when it laminates with B in the nip between the circularlygrooved hot lamination roller (10) and the rubber coated axiallygrooved, hot lamination roller (11). Since roller (13) is idling and thelaminate is taken off from this roller under a low tension, ply A willgradually shrink when it has passed this nip where lamination takesplace and while it still is on the hot lamination roller (10). Roller(13) is close to roller (10) without contacting it, thereby each fineflute in A will remain in its groove during the shrinkage, and thelatter will take place in a well ordered manner, producing regularflutes in B.

Roller (13) also serves to counteract or eliminate a tendency in thefinal laminate to curl around a transverse direction. This tendency ismainly due to tensions created by the shrinkage of ply A and ply B'sresistance to this. While the laminate follows roller (13), which asmentioned is a hot roller, it is bend oppositely, thereby counteractingthe effect of “differential shrinkage”. Furthermore the surface of (13)may be supplied with a very shallow pattern of circular groovesimparting the laminate with coarse and very shallow, longitudinallyextending waves, which completely can eliminate the tendency to curling.These waves can have a depth of e.g. 0.5-5 mm and a wavelength about10-20 times the depth. The laminate is air cooled while it leaves roller(13) under a low tension. Alternatively there may, prior to the cooling,be arranged further shrinkage while the laminate passes an oven heatedwith hot air.

With certain modification the line shown in FIGS. 17 and 18 can also beused to make the laminate of FIG. 16, which has second attenuated zones.For this purpose roller (6 a) should have the same profile and the samelow temperature as roller (7), and it should be preceded by and inslight engagement with a roller with the same surface profile as roller(8), which roller should have the same higher temperature as roller (8).

In another modification of the line shown in FIGS. 17 and 18 therubber-coated lamination roller (11) is not supplied with grooves but issmooth, and ply B is segmentally stretched in its machine directionprior to entering rollers 15 a and b so as to get “first attenuatedzones” perpendicular to the machine direction. The temperatures ofrollers (12) and (11) are adapted to the thickness of these zones andthe velocity of the ply in such a manner that the temperature in thezones becomes sufficient for a good bonding, while it remainsinsufficient outside the zones.

A technical equivalent of the rubber roller (11) in the processdescribed in connection with FIGS. 17 and 18 (not the process describeddirectly above) is a roller from microporous material supplied withaxial grooves and heated like the rubber roller, which in a well-knownmanner applies hot, compressed air forming a thin air film whichprevents contact between the crests of the roller and ply B, but allowsa similar lamination pressure as the rubber roller. The advantage isthat this air-lubricate roller does not abrade like the rubber roller.

The smooth rubber roller, which can substitute roller (11) when thefirst attenuated zones are present with suitably adapted heating cansimilarly be substituted by an air-lubricating, heated body, which doesnot need to rotate. Its surface may be concentric with roller 10,whereby particular high lamination velocities can be achieved.

In FIG. 20 which as mentioned shows a longitudinal section through aflute in ply A, both plies have been flattened and sealed to each otherat intervals (103) to form pockets or “mini-containers” and these mini-,containers have been filled with a particulate substance (104) which hasa purpose for the use of the laminate, e.g. for protection of materialpacked or wrapped up in the latter. As one among many options it may bean oxygen scavenger. To enhance the action of the substance the flutesmay be supplied with fine perforations on the side towards the packedproduct. The substance may also e.g. be a fire retardant material suchas CaCl₂ with crystal water, or just fine sand to increase the bulkdensity of the laminate.

FIG. 23 which shall be described below, shows how the particulatesubstance can be fed into the flutes of ply A prior to its laminationwith ply B, and how the flutes can be closed to pockets by transversesealing after the lamination, without any essential contamination ofthese transverse seals.

A laminate between a fluted thermoplastic film and a non-flutedthermoplastic film with a filling material between is known fromJP-A-07-276547 (Hino Masahito). However, in this case the fillingmaterial is a continuous porous sheet (for absorption) which extendsfrom flute to flute without interruptions, so that there is no directbonding between the flute and the non-fluted films. One of thethermoplastic films is first directly extruded into this porous (e.g.fibre-formed) sheet, then the two together are given a fluted shapebetween gear rollers while the thermoplastic film still is molten, andfinally a second thermoplastic film is extruded directly unto thisfluted assembly to join with the porous sheet. Hereby the bondingnecessarily must be very weak, and the mechanical characteristics mustbe completely different from those of the present product. Thewavelength of the fluting is not indicated.

In the technical filter material for liquid or gas flows shown in FIG.21 there is inserted a strand or yarn into each flute of A—in connectionwith the description of FIG. 23 it shall be explained how that can be,done—and both plies are supplied with rows of perforations, (106) in plyA and (107) in ply B. These rows are mutually displaced as shown so thatthe liquid or gas passing from one surface of the laminate to the other,is forced to follow a channel over a distance corresponding to thedisplacement. The fitting between the yarn and the channel may beimproved by shrinkage of A and/or B after the lamination process.

The pocket structure shown in FIG. 20 can also be used for filtrationpurposes if ply A and ply B are supplied with mutually displaced holes.Then the particulate substance (104) can e.g. consist of activecharcoal, or an ion-exchange resin, or for simple filtration ‘purposesfine sand. Also in this case a tightening of the passage by means ofshrinkage can be advantageous or may even be needed.

Practical examples of the use of such filter materials are for airfiltration systems including absorption of poisonous substances, andion-exchange processes. In both cases the laminate can have the form ofa long web which is slowly advanced transversely to flow which passesthrough it.

Another practical use is as a substitute of geotextiles e.g. for roadconstructions. Such textiles must allow water to penetrate but hold backeven fine particles. The present laminate, e.g. filled with fine sand inthe pockets, is suited for this use.

For such filtration purposes, high puncture strength will often beneeded, and the laminate then preferably comprises oriented,crosslaminated films.

The weather protective laminate shown in FIG. 22, e.g. for raincoats,also has a pocket structure, whereby ply A is heatsealed to ply B bytransverse seals as locations (103), but there is no particulatesubstance in the pockets. Like the laminate for filtration, each line ofpockets is supplied with perforations in a displaced system, here shownas groups of perforations (109) in A and similar groups (110) in B, andthese groups are mutually displaced. In this sketch it is consideredthat ply A is on the side where it rains, and a person, animal or item,which the laminate shall protect, is on the ply B side. (It could be theother way round). It is also considered that the direction shown byarrow (108) is upward. Since the perforations (109) are at the bottom ofthe pockets, and because of the gravity force, only the bottom of thepockets may be filled with rainwater, while in principle no water willreach the perforations (110). On the other hand there is free passage ofair and transpiration between the hole groups (109) and (110). Alaminate according to the invention, supplied with pockets andperforations on both sides, especially perforations near each boundaryof each pocket, can also find other important uses, e.g. it isconsidered suitable, when hydrophobic, to soak up a leaked oil film atsea.

The modification of the FIG. 18 machine-line shown in FIG. 23, isadapted to fill a particulate substance (104) into the channels formedbetween A and B. The filling is here shown very schematically. Thepowder (104) is taken from a hopper (111) and is administered by meansof an adjustable vibrator (not shown). It falls into the fluted ply A atthe upper side of the grooved lamination roller (10). At regular timeintervals hopper (111) is filled up with the powder (104). The means forthis are not shown. Other conventional systems for administering thepowder (104) onto ply A on roller (10) may of course be chosen.

Roller (10) vibrates (means not shown) so that the powder is moved fromthe higher zones, i.e. those which become bonded zones when A meets B inthe nip between (10) and (11), into the lower zones, which become the“channels”.

Having left the laminating rollers (10), (11) and roller (13), theA+B-laminate with powder (104) in the channels moves toward thecog-roller (113)—its surface is shown in a detailed part-drawing—and itsrubber-coated counter-roller (114) which together flatten and close thechannels by making transverse seals. Roller (113) is vibrated in orderto move powder away from the channel”: parts which become flattened andsealed.

Both rollers (113) and (114) are heated to a temperature needed for thesealing, and since the laminate while entering these rollers still isnear to temperature suitable for heatsealing due to the previoustemperatures, this second heatseal process needs not cause a slowingdown of the entire process.

For producing the product of FIG. 21, roller (113) and (114) can beomitted or taken out of function, and instead of administering powderinto ply A, there can at the same place be laid a yarn into each flute.Each yarn is taken from a separate reel.

At some stage after rollers (10)/(11), ply B may be subjected totransverse shrinkage. It may be necessary to hold the laminate at theedges while B shrinks. This may be done by’ means of an ordinary tenterframe, but the latter should be set up to work inversely so that thewidth gradually is reduced instead of increased.

The process for making the transversely pre-fluted ply B, which appearsfrom the flow-sheet FIG. 24 is generally analogous to the process whichis described in connection with FIGS. 17 and 18, and the profiles of thegrooved rollers can also be generally similar, except that for theprocess of FIG. 24 the grooves extend axially, while for the process ofFIGS. 17 and 18 they are circular.

Step 1: Transversely oriented ply B, which was made tension-less at thelamination temperature and then again cooled, is longitudinallystretched in very narrow zones localized on the tips of a hot rollerwhich has a profile similar to that of roller (8). The groovedcounter-roller, which is cold, has a profile like that of roller (7).

Step 2: The warm, stretched “second attenuated zones” are cooled on acold grooved roller which also has a profile like that of roller (7).Then to form “first attenuated zones” between the “second”, ply A islongitudinally stretched between this cold roller and a warm groovedroller which also has a profile similar to that of roller (8). Thestretching is localized to the tips of this roller. Similar to theregistration in printing technology, step 2 is brought in registrationwith step 1 under use of a device which optically’ detects the stretchedzones.

Step 3: The flutes are first formed in the grooves of a hot rubbercoated roller with a profile similar to that of roller (10), e.g. underuse of compressed air, and are held in the grooves e.g. under use ofvacuum, all as explained in connection with FIG. 25, and ply B is thenlaminated with ply A between the crests of this grooved rubber rollerand a circularly grooved steel roller, which also is heated. Ply A hasbeen preheated, and has already been supplied with flutes in the processshown in FIGS. 17 and 18.

There can be different after-treatments as explained in the foregoing,in particular after-shrinkage in one or both directions.

In FIG. 25, ply B which has been supplied first with the very narrowtransverse second attenuated zones (101), and then with the somewhatwider, also transverse first attenuated zones (6), is directed into thegrooves (115) of the heated lamination roller by means of compressed airfrom a row of nozzles of which one (116) is shown. By use ofregistration means, working on basis of optical detection of zones (6)or (101) it is arranged that the first attenuated zones (6) will coverthe crests (118) of the grooved roller. The two sets of attenuated zonesact as hinges so that even a quite heavy ply B may be bent and form theflutes. The latter are held in shape in the grooves under use of vacuumapplied through channels (117) from the interior of the roller. Thus plyB is moved in flute shape to the nip (not shown) between the groovedroller and the circularly grooved counter-roller, where lamination takesplace. One of the two rollers, preferably that which feeds B, is rubbercoated. The vacuum in the grooves is adjusted so that ply A is heldfirmly when this is needed, but can be released where that is needed.There can also be a valve arrangement inside the grooved roller toeliminate the vacuum during the release.

It is noted that FIG. 25 also, with some modifications, can illustrate amethod of making the first and/or second attenuated zones (8) and (101)transverse to the machine direction by a new kind of segmentalstretching ego as an alternative to steps 1 and/or 2 in the flow-sheetFIG. 24. For this purpose the roller, which now acts in analogy toroller (8) in FIGS. 17 and 18 (but making transverse stretching zones)should be heated similar to roller (8) and have relatively “sharp”crests also like the latter (e.g. radius of curvature 0.7 mm) in orderto localise the stretching to material in contact with or close to thecrests. Furthermore the simple administration of compressed air fromnozzles (116) should be substituted by a “Hover-craft” air pillow systemto set-up an air pressure of several bars, capable of stretching the plyover the crests of the roller. Under special circumstances, when apressure difference below 1 atm is sufficient, it will also be possibleto stretch the ply over the crests of the roller by vacuum-forming. Thevacuum is applied through channels (117).

In FIG. 26, hole (106) represents one series of holes on one side, andhole (107) represents another series of holes on the other side of thelaminate, and the two series of holes are mutually displaced, so that aflow of gaseous or liquid material entering from one side through holes(106) must divide out and follow channels formed by the two sets offlutes, before the flow can reach holes (107) and exit on the other sideof the laminate. Hereby hydrophobic or ‘hydrophilic properties of thechannel walls can be advantageously utilized as explained in the generalpart of this specification.

FIG. 26 is a simplified presentation, since it only shows two mutuallydisplaced holes, and only 4 wavelengths total passageway from hole tohole, i.e. generally about 3-10 mm total passageway. In practice it ismore convenient to make “twin” or “triplet” holes, as this will beexplained in connection with FIGS. 27 and 27 a, and also create asomewhat longer total passageway. This embodiment of the inventionpresents an entirely new type of porosity, with high regularity, whichcan be expected to find several important applications.

FIGS. 27 and 27 a are identical except for the orientation of theslightly protruding flat spikes, (205) in FIG. 27 and (202) in FIG. 27a. The metal parts (201) of the rollers including the spikes which arefixed, for instance screwed, into this part are heated to a temperaturewell beyond the melting range of the polymer material. The rollersurface is covered by heat insulating material, here shown as smallplates (203) which e.g. can be made from poly(tetrafluoroethylene)(Teflon trade mark). There is one such plate per spike, and each isfixed onto the metal surface by means of the spike. The edge of the flatspike protrudes less than 1 mm from the outer level of the DTFE plate,so that it can touch the flutes on one side of the laminate withoutpenetrating to the outer side Of the laminate.

The laminate is caused to follow the roller over a short distance at thesame or almost the same velocity as the latter. There may be a verysmall difference between the velocities in order to widen the holes. Inorder to press the laminate towards the spikes, which cut and meltholes, and at the same time protect the ply, which should not becomeperforated in that process step, air jets are blown towards the laminatethrough holes in the pipes (204). The spikes (202) and (205) arearranged in a pattern of rows, both circumferentially and axially, andthe holes (204) in the pipes correspond with each of the circumferentialrows so that the air pressure and the cooling effect become highestwhere most needed.

The spikes in FIG. 27 can be of identical shape with those in FIG. 27 a,namely wedge-formed with the shape which appears when the two figuresare studies together. The sharp edge cuts perpendicular to the directionof the flutes in both cases, and the length of this edge canconveniently correspond to two or three times the wavelength of theflutes so that “twin” or “triplet” holes are formed.

Outside the area where the roller contacts the laminate, air of ambienttemperature is blown out onto the PTFE platelets to keep their surfaceat a temperature below the melting range of the polymer material (themeans are not shown).

Example 1

A 2-ply laminate of ply A and ply B with A longitudinally and B,transversely fluted and oriented was manufactured on a pilot unitconstructed as shown in FIGS. 17 and 18. Both plies consisted of onecoextruded, cold-stretched 0.037 mm thick film consisting of HDPE with athin layer on one side consisting of an ethylene copolymer having amelting range between 95-105° C. This was used as lamination layer inthe process. The cold-stretching was carried out near room temperatureat a draw ratio about 3:1 and was followed by heat stabilisation, all bywell-known means, and while the film had flat tubular form. The tube waslongitudinally cut to form ply A.

Processes for continuous manufacture of transversely oriented film arewell known and mentioned in the foregoing, but it would have causedpractical complications for the inventor to, have such film manufacturedaccording to his specifications, and therefore short lengths of the plyA-film were heat-sealed together edge to edge to form a transverselyoriented web.

All of the grooved rollers had the pitch 1.1000 mm at the temperature atwhich they actually were used, but due to the large temperaturedifferences during the stretching laminating process, the thermalexpansion had to be taken into consideration when these rollers weremachined at 20° C., see the table below. The biggest temperaturedifference between the rollers, as it appears from this table, was 85°,and this corresponds to an expansion of about 0.10 mm per 10 cm rollerlength, while the accumulated error in the fitting between adjacentrollers from end to end of the rollers must be maintained lower than0.10 mm to obtain the needed registration.

The table below also indicates the radius of curvature (R) or the lengthof a land on the crest of the grooved rollers as seen in the axialsection in FIG. 17 and indicated in mm.

Roller No. 6a 7 8 9 10 11 Crest land R R R land land mm 0.4 0.2 0.7 0.150.4 1.0 Temp ° C. 70 20 70 105 105 105 Pitch mm 1.0993 1.1000 1.09931.0988 1.0988 2.0

The roller (12) for preheating and stabilisation (shrinkage) of B washeated to 90° C.

It is of course not practically possible to achieve such a high accuracyin the pitch of rollers (6 a) to (10) seen individually from groove togroove, but it is essential that errors in the pitch do not accumulateby more than 0.05 mm. This is best achieved when the surface parts aremade from segments and accumulated errors are eliminated by finegrinding of the segment ends and/or thin shims (foils) are insertedbetween the segments. In the actual pilot machine the length of thegrooved part of each roller surface was about 450 mm and was assembledfrom 3 segments. It is judged that in an industrial machine the rollerscan be made in up to about 5 m length, but in that case the accuracyfrom end to end has to be checked with laser measurements andadjustments made as explained.

The main part of the transverse stretching, which is the basis for theflute formation in A and which forms the first attenuated zones—laterthe zones which become bases, not crests of the flutes in thelaminate—took place by the intermeshing between rollers (7) and (8) andbecame localized to a zone on and nearby the crests of roller (8). Thisis because roller (8) was hot and had a relatively sharp crest, whileroller (7) was cold and had a much rounder crest (higher radius ofcurvature R). It is relevant also in this connection that ply A wasuniaxially oriented in the machine direction and therefore had a hightendency to “neck-down” and form sharply delimited attenuated zones whenit was transversely stretched.

The function of roller (6 a) was to preheat the zones which were to bestretched on the tips of roller (8). In this example the “land” on thecrests of roller (6 a) are wider than the diameter of the crests ofroller (8). This has been chosen in order to counteract the pronouncedtendency in the film to neck-down, in other words, to make the limits ofthe first attenuated zones smoother. In other cases e.g. when ply A hasa pronounced transverse orientation and therefore no tendency to neckingdown by transverse stretching, the land on the crests of roller (6 a)which preheats the film, should be no wider than the land on the crestsof roller (8).

Between rollers (6 a) and (7) there was set a slight but almost zeroengagement to avoid wrinkles, but without stretching the films.

Having left the transverse stretching roller (8), ply A was taken overby transfer roller (9). This had the high temperature shown in order tohelp the shaping of flutes in the zones which had not been stretched. Atthis stage the first attenuated zones were still deeply curved, but when(A) was taken over by the flat 0.4 mm wide crests (lands) on the groovedlaminating roller (10) the first attenuated zones were flattened almostover their entire width except at their boundaries where the thicknessgradually increases. The rubber-coated counter-roller, was heated fromits inside by circulating water like the other heated rollers, andfurthermore was heated from outside with hot air to keep the surface ata temperature of 105° C.

Prior to the experimental run the axial positions of the grooved rollerswere very carefully adjusted to each other, and so was the intermeshingbetween adjacent grooved rollers. The intermeshing between rollers (7)and (8) was set to make the depth of the fluting 0.40 mm, as measured inmicroscope on a cross-section of the finished laminate. As alreadymentioned, the engagement between rollers (6 a) and (7) was set toalmost zero. The engagement of roller (8) to roller (9) and of roller(9) to roller (10) was set to exactly zero. The pitch of the deeplygrooved rollers (14 a) and (14 b) was 10 mm. Their intermeshment was setto allow maximum shrinkage of ply B in the direction perpendicular tothe machine direction, without causing any folds or pleats in the finalstate of this ply.

Rollers (6 a) to (10), roller (12) and rollers (14 a and b) were alldriven at the same circumferential velocity, while roller (11) wasdriven by roller (10) and the other rollers were idling.

By the heating of ply (A) on rollers (8), (9) and (10) it acquired ahigh ‘tendency to longitudinal shrinkage but was kept tentered until itpassed the nip between rollers (10) and (11) and thereby becamespot-laminated to ply (B). Then while still on roller (10) it developedits shrinkage and caused ply (13) to buckle up, forming its flutes.

The idling take-off roller (13) had a heat insulating surface so thatthe laminate still to some extent was formable on this roller. Theroller surface was slightly corrugated, namely in a waving which seen inaxial section had sinus form with wavelength 10 mm and depth 1.0 mm.This essentially eliminated the tendency of the laminate to curl.

While leaving roller (13) under a low tension the laminate wasair-cooled. Measurements showed that ply A had contracted 20% after thelamination step, and ply B has buckled up correspondingly. The height ofthese flutes was measured to be 0.5 mm.

Example 2

The procedure of example 1 was repeated with the difference that thedivision of axial grooves on the rubber coated lamination roller ischanged from 2.0 mm to 1.0 mm with the land being 0.5 mm. This alsoproduces flutes in B by the shrinkage of A. The height of these flutesis measured to be 0.25 mm.

Example 3

The film produced as explained in example 1 was air-heated to 115° C.while the edges parallel to ply A's flutes were fixed between clamps,which however were set up so that they allowed ply B freely to shrinkHereby the wavelength in ply A was reduced to 0.8 mm.

Example 4

The laminate of example 1 was subjected to the procedure explained inconnection with FIGS. 27 and 27 a, however since the two rollers forperforation were only about 400 mm long and constructed for shortexperimental runs its was possible to simplify this construction. Thewedge formed spikes (202) and (205) were made as one part with the steelsleeve (201) of each roller. Furthermore the many Teflon plates weresubstituted by a simple coating with a 2-component epoxy binder. Theedges of the wedge-formed spikes extended 0.2 mm beyond this coating.The length of this edge was 5 mm. The temperature of the edge was about150° C. and the temperature on the surface of the epoxy cover about 120°C. The distance from a spike to each of its 4 neighbors was 40 mm,measured from edge-middle to edge-middle.

The laminate was first perforated on one side to form a first pattern ofperforations, then in a second separate process on the other side toform a second pattern of perforations. During this second process it wasmanually controlled that the second pattern of perforations fittedcorrectly with the first pattern to give maximum displacement betweenthe two patterns. (In practical production the second series ofperforations should of course be carried out in line with the firstseries).

The laminate with mutually displaced patterns of perforations on its twosides was converted to a small bag and there was filled about 10 cmwater into the bag, which was suspended in a set of frames holding thebottom straight horizontally and allowing the water to drop down.

The water continued to drop until its surface stood 20 mm over thebottom, then it stopped dropping. It can be concluded that the finecapillary channels in the laminate could withstand 20 mm water pressuredue to their fineness and hydrophobic properties. It is noted that thelaminate of my copending patent application WO-A-021 02592 mentioned inthe introduction, in which ply A is fluted and ply B flat, has beenfound to show similar properties when the flutes are similarly fine, theperforations are similarly arranged, and the material is similarlyhydrophobic. However in that case the perforations in ply B (the flatply) cannot be made in the same, very practical way.

Example 5

This example illustrates use of shrinkage of longitudinally oriented plyA to produce a 2-ply NB in which A is non-fluted and B is transverselyfluted. The procedure is the same as in example 1 except for theimportant difference that rollers (6 a), (7), (8), (9) and (10) areexchanged by smooth rollers (reference numbers here remain the same) androller (6 a) is supplied with a rubber counter-roller to prevent thefilm from slipping over it. The rubber-coated roller (11) is the same asin example 1, i.e, it is supplied with axial grooves of pitch 2.0 mm andland 1.0 mm’ (In this case the same effect can be achieved when therubber coated roller (11) is flat and the matching steel roller (10) issupplied with axial grooves of pitch 2.0 mm and land 1.0 mm).

Rollers (6 a) and (7) are kept at room temperature while rollers (8),(9), (10) and (11) are controlled at the lamination temperature 105° C.,and the temperature of roller (12) which preheats ply B and due to thepleats introduced by rollers 14 a and b essentially eliminates itstendency to transverse shrinkage, is controlled at 90° C.

The composition of both plies, and the cold stretching prior to the “figprocess” is exactly as in example 1. Like in that example the transverseorientation in ply B is achieved by welding short lengths oflongitudinally oriented film together.

Rollers (6 a) to (10), roller (12) and rollers (14 a and b) are alldriven at the same circumferential velocity, while roller (11) is drivenby roller (10) and the other rollers are idling.

By the heating of ply (A) on rollers (8), (9) and (10) it acquires ahigh tendency to longitudinal shrinkage, but since counter-rollers hold(A) firmly to rollers (6 a) and (10) the shrinkage takes place after thelamination with ply B, and since the bonding is established alongtransverse linear areas, this shrinkage causes B to “buckle up” toflutes between the bonded areas. This also gives the laminate a tendencyto curling but that tendency is essentially eliminated by roller (13)due to its slightly waved surface.

The final laminate consists of flat longitudinally oriented ply A andtransversely fluted, transversely oriented ply B. The wavelength of theflutes is about 1.5 mm.

I claim:
 1. A method of manufacturing a laminate comprising: fluting a ply A using first grooved fluting rollers to impart a first fluted configuration to the ply A to form a fluted ply A, first solid-state stretching the fluted ply A between first grooved stretching rollers to form first attenuated zones disposed parallel to a flute direction of the stretched fluted ply A, where the stretching occurs perpendicular or substantially perpendicular to the flute direction, and laminating the fluted ply A to a ply B using heat and pressure to adhesively bond a first side of the ply B to a first side of the ply A using laminating rollers to form a laminate having bonding zones, where each grooved stretching roller is different from each laminating roller, and where each laminating roller is coordinated with each grooved stretching roller so that the bonding zones are disposed substantially within the first attenuated zones, and where a wavelength of the flutes of the fluted ply A is less than or equal to about 5 mm.
 2. The method of claim 1, wherein the ply B is flat and the bonding zones comprise regions of the ply B that contact crests of the fluted ply A.
 3. The method of claim 1, further comprising: prior to the fluting, orienting the ply A in one or both directions so that a main direction of orientation in the oriented ply is substantially the same as the flute direction of the ply, after laminating, thermally shrinking the fluted ply A in a direction substantially the same as the flute direction of the flute ply A to form flutes in the ply B, where a flute direction of the fluted ply B make an angle with the flute direction of the fluted ply A, wherein at least one oldie laminating rollers is grooved, the bonding zones comprise spotbonds between crests on the first side of the ply A and crests on the first side of the ply B, and wavelengths of the flutes of the plies A and B are less than or equal to about 10 mm, and the wavelength of the flutes in at least one of the plies A or B is less than or equal to about 5 mm.
 4. The method of claim 3, further comprising: prior to the laminating, first solid-state stretching the ply B between the first grooved stretching rollers to form first attenuated zones disposed parallel to a flute direction of the stretched ply B, where the stretching occurs perpendicular or substantially perpendicular to the flute direction of ply A, where each grooved stretching roller is different from each laminating roller, and where each grooved laminating roller is coordinated with each grooved stretching roller so that the bonding zones are disposed substantially within the first attenuated zones.
 5. The method of claim 4, further comprising: prior to or after the formation of the first attenuated zones, second solid-state stretching at least one of the fluted ply A or ply B between second grooved stretching rollers to form second attenuated zones in the fluted ply A or the ply B both of which have the first attenuated zones, where the second attenuated zone are parallel with the first attenuated zones, where the second attenuated zones are narrower than the first attenuated zones, and where the second grooved stretching rollers are coordinated with the first grooved stretching rollers so that the second attenuated zones are disposed substantially between neighboring first attenuated zones.
 6. The method of claim 5, wherein each grooved roller used to form the flutes in one of the plies and each grooved roller used to form the first attenuated zones in both the fluted ply A and the ply B, and each grooved roller used to form the second attenuated zones in the fluted ply A and/or the ply B, and a grooved roller which the plies follow before and during lamination, if present, are rollers in which the grooves are substantially parallel with the roller axis, and means are provided to hold the flutes of the fluted ply A in the respective grooves during the passage from the position where the flutes are formed to the position where lamination takes place, the holding means adapted to avoid a frictional rubbing on the plies during the passage.
 7. The method of claim 5, wherein the second attenuated zones are formed by grooved rollers acting in coordination with the first grooved stretching rollers, and the coordination comprises an automatic fine regulation of relative velocities between the rollers.
 8. The method of claim 4, wherein the adhesive bonding is directly between the ply A and the ply B and established through a lamination layer on at least one of these plies, and where the lamination layer is heated to a lamination temperature by heating from an opposite side of the fluted ply A and/or the ply B, wherein a temperature of the laminating rollers and a thickness of the fluted ply A and/or the ply B in the first attenuated zones of both fluted ply A and ply B allow the lamination layer to reach the lamination temperature, while a thickness of the fluted ply A and/or the ply B outside the first attenuated zones of both fluted ply A and ply B in contact with crests of the grooved laminating roller is such that the lamination layer outside the first attenuated zones of both the fluted ply A and the ply B do not reach the lamination temperature and where the first attenuated zones of both fluted ply A and ply B and the bonding zones become substantially coincident.
 9. The method of claim 8, wherein a pitch of the grooved lamination roller less than or equal to 3.0 mm.
 10. The method of claim 8, wherein the fluting step, which establishes the flute configuration in one of the plies A or B substantially in a machine direction comprises taking one of the plies A or B before laminating through a set of driven mutually intermeshing grooved rollers, the grooves on the rollers being circular or helical and forming an angle of at least 60° with the roller axis.
 11. The method of claim 10, wherein one of the plies A or B passing directly from its exit from the last of the grooved stretching rollers and grooved fluting rollers to the grooved laminating roller, these two mutually intermeshing grooved rollers being in close proximity to each other and having the same pitch when measured at each ones operational temperature and being mutually adjusted in the axial direction for alignment of the grooves.
 12. The method of claim 8, wherein the ply A and/or the ply B passing from its exit from the last of the grooved fluting rollers to the grooved laminating roller over one or a series of heated, grooved transfer rollers, the grooved rollers in the row starting with the grooved stretching rollers and ending with the grooved laminating roller each being in close proximity to its neighbor or neighbors, whereby each of the grooved rollers in the row has the same pitch when measured at their respective operational temperature, and being mutually adjusted in the axial direction for alignment of the grooves.
 13. The method of claim 4, further comprising: forming a distinct stripe formation in the first attenuated zone zones of both the fluted ply A and the ply B, where the stripes are established at least in part by giving the crests on the grooved stretching roller intended to produce the stripes a temperature higher than a temperature on the crests of the other grooved stretching roller and/or by giving the crests on the grooved stretching roller intended to produce the stripes a radius of curvature smaller than a radius of curvature of the crests on the matching grooved stretching roller.
 14. The method of claim 4, wherein the first attenuated zones are formed by grooved rollers acting in coordination with the grooved laminating roller used and the coordination comprises an automatic fine regulation of relative velocities between the rollers.
 15. The method of claim 3, wherein at least a part of a depth of each flute in at least one of the two plies A or B, is carried out after lamination by thermal shrinking one of the plies A or B in a direction substantially perpendicular to the flute direction of the other ply.
 16. The method of claim 3, further comprising: after the lamination, flattening at least some of the flutes in each ply in locations placed at intervals and subjecting each ply to heat and pressure sufficient to bond the plies to each other in the locations so that the two arrays of flutes together form channels or closed pockets.
 17. The method of claim 16, wherein at least some of the flattening is carried out with bars or cogs which have their longitudinal direction arranged substantially in the machine direction and/or a direction transverse thereto.
 18. The method of claim 16, wherein particulate, liquid, fiber or yarn material is filled into some at least of the channels formed by the two arrays of flutes, this filling taking place prior to or during laminating.
 19. The method of claim 18, further comprising: after filling, the filled channels are closed at intervals by pressure and heat to form filled pockets.
 20. The method of claim 19, further comprising: prior to, simultaneously with or following the filling step perforating the pockets at least on one side to facilitate the filling material or part thereof to dissipate into the surroundings or to allow air or liquid to pass through the filling material.
 21. The method of claim 16, further comprising: forming a multitude of perforations in the two plies A and B, but limited to areas, where the two plies are not bonded together, and the perforations in the ply A are displaced from the perforations in the ply B to force air or liquid which passes through the laminate to run a distance along one or more channels.
 22. The method of claim 3, further comprising: melting a multitude of holes in the ply A, but not in the ply B or in the ply B, but not in the ply A, where the holes are formed by contacting flutes of the ply A or B with protruding surface parts of a hot roller, where the parts are moving at substantially the same velocity as the laminating rollers.
 23. The method of claim 22, wherein the holes are formed by contacting flutes of the second ply with protruding, surface parts of a hot roller, which are moved at substantially the same velocity as the laminating roller, while heat insulating material prevents the flutes from contacting the hot surfaces of the hot roller.
 24. The method of claim 23, further comprising: drawing a protruding nap of fibre-like film portions out from the molten surroundings of holes by blowing air in between the laminate and a hot roller, where the laminate leaves the hot roller.
 25. The method of claim 1, wherein the adhesive bonding is i) directly between the ply A and the ply B and established through a lamination layer on at least one of these plies; ii) established through a separate thin bonding film; or iii) established through a fibrous web including surface bonding layers.
 26. The method of claim 1, wherein the ply A comprises a monofilm-formed ply or multifilm-formed ply and/or the ply B comprises a monofilm-formed ply or multifilm-formed ply and the plies A and B comprise polymeric materials that are orientable at room temperature.
 27. The method of claim 1, wherein the plies A and B comprise polyolefins.
 28. The method of claim 1, wherein the ply A comprises a main layer and a lower melting surface layer on the first side of the ply A, wherein the ply B comprises a main layer and optionally a lower melting point layer on the first side of the ply B, and wherein the ply A is co-extruded prior to fluting and if the ply B includes the lower melting point layer, then the ply B is co-extruded prior to laminating.
 29. The method of claim 1, further comprising: prior to the fluting, orienting the film or films constituting at least one of the plies A or B in one or both directions so that a main direction of orientation in the oriented ply is substantially the same as the flute direction of the ply A and/or the ply B.
 30. A method of manufacturing a laminate of a first ply with a second ply both comprising an orientable thermoplastic polymer material and each having one face comprising a lamination layer in which the first and second plies are continuously fed in face to face relationship with the lamination layers in direct contact with one another between a pair of laminating rollers between which heat and pressure is applied, whereby the lamination layers become adhered to one another, in which the second ply is oriented substantially transversely of a machine direction, and is substantially non-shrinkable in solid state in a direction transverse to its orientation, and the first ply as it is fed to the laminating rollers is heat-shrinkable substantially in a shrink direction which is substantially parallel with the machine direction, the laminating rollers apply heat and pressure in bonding zones arranged in continuous or discontinuous rectilinear lines extending in a direction which is generally perpendicular to the shrink direction, and after lamination, the first ply is caused to shrink in a solid state or semisolid state in the shrink direction, where the second ply becomes fluted with flutes extending perpendicular to the shrink direction and having a wavelength less than or equal to about 5 mm.
 31. The method of claim 30, wherein the wavelength is less than or equal to about 3 mm.
 32. The method of claim 30, wherein the first ply is kept substantially flat throughout the manufacturing process.
 33. The method of claim 30, wherein the first ply is supplied with waves prior to the lamination, the wavelength being less than or equal to about 3 mm, and the lamination zones are on crests on one side of the waved first ply.
 34. The method of claim 30, wherein by use of a take-off roller (13) having a slightly waved surface, the laminate on its whole is supplied with a longitudinal waving to eliminate a tendency to curling around its transverse direction.
 35. The method according to claim 30 in which said rectilinear lines are discontinuous and in which the discontinuities in adjacent lines are aligned in the shrink direction.
 36. A method of manufacturing a laminate of a first ply with a second ply both comprising an orientable thermoplastic polymer material and each having one face comprising a lamination layer in which the first and second plies are continuously fed in face to face relationship with the lamination layers in direct contact with one another between a set of laminating devices between which heat and pressure is applied, whereby the lamination layers become adhered to one another, in which the second ply is oriented substantially transversely of a machine direction, and is substantially non-shrinkable in solid state in a direction transverse to its orientation, and is prior to the laminating devices, segmentally stretched in its machine direction to introduce first attenuated zones perpendicular to the machine direction, the first ply as it is fed to the laminating devices is heat-shrinkable substantially in a shrink direction which is substantially parallel with the machine direction, the laminating devices comprise on the side facing the second ply a heated flat roller or a heated porous bar adapted to produce a film of hot air to press the plies towards the opposite laminating devices, which may be either a roller or a similar bar, a speed of the machine and temperatures of the rollers being adapted to heat the lamination layer in the first attenuated zones to a lamination temperature, but not to heat the lamination layer in adjacent non-attenuated zones to the lamination temperature, where bonding takes place only in the first attenuated zones, and after lamination, the first ply is caused to shrink in the solid state or the semisolid state in the shrink direction, where the second ply becomes fluted with flutes extending perpendicular to the shrink direction and having a wavelength less than or equal to about 5 mm.
 37. The method of claim 36, wherein the wavelength is less than or equal to about 3 mm.
 38. The method of claim 36, wherein the first ply is kept substantially flat throughout the manufacturing process.
 39. The method of claim 36, wherein the First ply is supplied with waves prior to the lamination, the wavelength being less than or equal to about 3 mm, and the lamination zones are on crests on one side of the waved first ply.
 40. The method of claim 36, wherein by use of a take-off roller (13) having a slightly waved surface, the laminate on its whole is supplied with a longitudinal waving to eliminate a tendency to curling around its transverse direction.
 41. The method according to claim 36 in which said rectilinear lines are discontinuous and in which the discontinuities in adjacent lines are aligned in the shrink direction. 